Pessoal, estou tendo o seguinte problema relacionado a migração do um projeto Eclipse ADT para o Android Studio.
18:20:42 Gradle sync started
18:20:43 Gradle sync failed: Cause: failed to find target with hash string 'android-21' in: G:\AppData\Local\Android\Sdk
Consult IDE log for more details (Help | Show Log)

O Android instalado e a versão 6

Alterei a versão do compileSdkVersion para a versão do SDK instalada compileSdkVersion 23
E o erro passou a ser o seguinte:
Error:Execution failed for task ':app:processDebugManifest'.
> Manifest merger failed with multiple errors, see logs
Android Monitor:
03-18 21:07:13.640 2170-2930/com.google.android.gms.persistent E/Auth: [GoogleAccountDataServiceImpl] getToken() failed. Status BAD_AUTHENTICATION, Account: <ELLIDED:-818113082>, App: com.google.android.gms, Service: oauth2:https://www.googleapis.com/auth/contextcontroller
com.google.android.gms.auth.be.account.b.d: Long live credential not available.
at com.google.android.gms.auth.be.account.b.e.a(SourceFile:105)
at com.google.android.gms.auth.be.p.a(SourceFile:355)
at com.google.android.gms.auth.be.o.a(SourceFile:260)
at com.google.android.gms.auth.firstparty.dataservice.y.a(SourceFile:197)
at com.google.android.gms.auth.firstparty.dataservice.x.a(SourceFile:558)
at com.google.android.gms.auth.firstparty.dataservice.x.a(SourceFile:196)
at com.google.android.gms.auth.o.a(SourceFile:276)
at com.google.android.gms.auth.o.a(SourceFile:196)
at com.google.android.gms.auth.t.a(SourceFile:498)
at com.google.android.gms.auth.s.a(SourceFile:908)
at com.google.android.gms.auth.s.e(SourceFile:528)
at com.google.android.gms.auth.s.d(SourceFile:450)
at com.google.android.gms.auth.q.c(SourceFile:588)
at com.google.android.gms.common.server.a.a.a(SourceFile:82)
at com.google.android.gms.common.server.c.a(SourceFile:59)
at com.google.android.gms.common.server.s.a(SourceFile:61)
at com.google.android.gms.common.server.s.a(SourceFile:139)
at com.google.android.contextmanager.l.a.a.a(SourceFile:130)
at com.google.android.contextmanager.g.a.a.run(SourceFile:52)
at com.google.android.contextmanager.g.i.a(SourceFile:263)
at com.google.android.contextmanager.g.i.handleMessage(SourceFile:254)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.os.HandlerThread.run(HandlerThread.java:61)
03-18 21:07:13.760 2170-2930/com.google.android.gms.persistent W/AuthSessionAuthenticato: Auth related exception is being ignored: BadAuthentication
03-18 21:07:13.790 2170-2930/com.google.android.gms.persistent W/ctxmgr: [DeviceRegistrationSync]Failed device registration sync (statusCode=UNKNOWN). Giving up.
03-18 21:10:37.520 1363-1376/system_process I/UsageStatsService: User[0] Flushing usage stats to disk
03-18 21:15:11.460 2776-2782/com.google.android.gms.unstable I/art: Debugger is no longer active
03-18 21:15:11.460 2052-2058/com.google.process.gapps I/art: Debugger is no longer active
03-18 21:15:11.460 2157-2163/com.google.android.googlequicksearchbox I/art: Debugger is no longer active
03-18 21:15:11.460 2299-2305/com.google.android.gms I/art: Debugger is no longer active
03-18 21:15:11.460 3010-3016/com.android.defcontainer I/art: Debugger is no longer active
03-18 21:15:11.460 2534-2540/com.android.providers.calendar I/art: Debugger is no longer active
03-18 21:15:11.460 1846-1853/com.android.inputmethod.latin I/art: Debugger is no longer active
03-18 21:15:11.460 1363-1369/system_process I/art: Debugger is no longer active
03-18 21:15:11.470 2170-2176/com.google.android.gms.persistent I/art: Debugger is no longer active
03-18 21:15:11.470 1833-1839/com.google.android.googlequicksearchbox:interactor I/art: Debugger is no longer active
03-18 21:15:11.470 1593-1595/com.android.systemui I/art: Debugger is no longer active
03-18 21:15:11.470 2548-2554/com.android.deskclock I/art: Debugger is no longer active
03-18 21:15:11.470 1616-1622/android.process.acore I/art: Debugger is no longer active
03-18 21:15:11.470 1932-1938/com.google.android.googlequicksearchbox:search I/art: Debugger is no longer active
03-18 21:15:11.470 3075-3082/com.example.milton.appteste I/art: Debugger is no longer active
03-18 21:15:11.470 1861-1872/com.android.phone I/art: Debugger is no longer active
03-18 21:15:11.470 3045-3051/com.svox.pico I/art: Debugger is no longer active
03-18 21:18:37.870 2170-2170/com.google.android.gms.persistent I/GoogleURLConnFactory: Using platform SSLCertificateSocketFactory
03-18 21:18:37.900 1021-1781/? D/WVCdm: Instantiating CDM.
03-18 21:18:37.900 1021-1790/? I/WVCdm: CdmEngine::OpenSession
03-18 21:18:37.900 1021-1790/? I/WVCdm: Level3 Library Sep 28 2015 13:08:28
03-18 21:18:37.900 1021-1790/? W/WVCdm: Could not read /data/mediadrm/IDM1013/ay64.dat2: No such file or directory
03-18 21:18:37.900 1021-1790/? W/WVCdm: Could not load liboemcrypto.so. Falling back to L3. dlopen failed: library "liboemcrypto.so" not found
03-18 21:18:37.900 1021-1790/? I/WVCdm: CdmEngine::QueryKeyControlInfo
03-18 21:18:37.900 1021-1021/? W/WVCdm: BufferReader::Read<T> : Failure during parse: Not enough bytes (4)
03-18 21:18:37.900 1021-1021/? W/WVCdm: CdmEngine::ExtractWidevinePssh: Unable to read atom size.
03-18 21:18:37.900 1021-1021/? I/WVCdm: CdmEngine::GenerateKeyRequest
03-18 21:18:37.900 1021-1021/? D/WVCdm: PrepareKeyRequest: nonce=3156899157
03-18 21:18:37.920 1363-2823/system_process I/AccountManagerService: getTypesVisibleToCaller: isPermitted? true
03-18 21:18:37.920 2776-2787/com.google.android.gms.unstable I/GoogleURLConnFactory: Using platform SSLCertificateSocketFactory
03-18 21:18:38.000 2170-29916/com.google.android.gms.persistent I/PhenotypeConfigurator: Scheduling Phenotype every 14400 seconds, with flex of 1800 seconds
03-18 21:18:38.030 1021-1437/? I/WVCdm: CdmEngine::CloseSession
03-18 21:18:38.060 1363-2624/system_process I/AccountManagerService: getTypesVisibleToCaller: isPermitted? true
03-18 21:18:38.330 2776-2787/com.google.android.gms.unstable I/art: Rejecting re-init on previously-failed class java.lang.Class<com.google.ccc.abuse.droidguard.DroidGuard>
03-18 21:18:38.370 1363-1494/system_process I/AccountManagerService: getTypesVisibleToCaller: isPermitted? true
03-18 21:18:38.470 2170-29916/com.google.android.gms.persistent I/PhenotypeFlagCommitter: Experiment Configs successfully retrieved for com.google.android.gms.phenotype
03-18 21:18:38.530 2170-29927/com.google.android.gms.persistent I/PhenotypeFlagCommitter: Experiment Configs successfully retrieved for com.google.android.gms.phenotype
03-18 21:18:38.550 1021-1437/? I/WVCdm: CdmEngine::OpenSession
03-18 21:18:38.550 1021-1437/? I/WVCdm: Level3 Library Sep 28 2015 13:08:28
03-18 21:18:38.550 1021-1437/? W/WVCdm: Could not read /data/mediadrm/IDM1013/ay64.dat2: No such file or directory
03-18 21:18:38.550 1021-1437/? W/WVCdm: Could not load liboemcrypto.so. Falling back to L3. dlopen failed: library "liboemcrypto.so" not found
03-18 21:18:38.550 1021-1437/? I/WVCdm: CdmEngine::QueryKeyControlInfo
03-18 21:18:38.550 1021-1276/? W/WVCdm: BufferReader::Read<T> : Failure during parse: Not enough bytes (4)
03-18 21:18:38.550 1021-1276/? W/WVCdm: CdmEngine::ExtractWidevinePssh: Unable to read atom size.
03-18 21:18:38.550 1021-1276/? I/WVCdm: CdmEngine::GenerateKeyRequest
03-18 21:18:38.550 1021-1276/? D/WVCdm: PrepareKeyRequest: nonce=26293087
03-18 21:18:38.640 1021-1790/? I/WVCdm: CdmEngine::CloseSession
03-18 21:18:38.890 2170-29915/com.google.android.gms.persistent W/GLSUser: [AppCertManager] IOException while requesting key:
java.io.IOException: Invalid device key response.
at com.google.android.gms.auth.be.appcert.a.a(SourceFile:268)
at com.google.android.gms.auth.be.appcert.a.a(SourceFile:132)
at com.google.android.gms.auth.be.appcert.b.a(SourceFile:43)
at com.google.android.gms.auth.b.b.a(SourceFile:62)
at com.google.android.gms.auth.b.a.a(SourceFile:120)
at com.google.android.gms.auth.b.a.a(SourceFile:61)
at com.google.android.gms.auth.be.cron.AuthCronService.a(SourceFile:44)
at com.google.android.gms.gcm.au.run(SourceFile:140)
03-18 21:21:01.380 1363-1379/system_process E/BluetoothAdapter: Bluetooth binder is null
03-18 21:21:01.380 1363-1379/system_process E/KernelCpuSpeedReader: Failed to read cpu-freq
java.io.FileNotFoundException: /sys/devices/system/cpu/cpu0/cpufreq/stats/time_in_state: open failed: ENOENT (No such file or directory)
at libcore.io.IoBridge.open(IoBridge.java:452)
at java.io.FileInputStream.<init>(FileInputStream.java:76)
at java.io.FileInputStream.<init>(FileInputStream.java:103)
at java.io.FileReader.<init>(FileReader.java:66)
at com.android.internal.os.KernelCpuSpeedReader.readDelta(KernelCpuSpeedReader.java:49)
at com.android.internal.os.BatteryStatsImpl.updateCpuTimeLocked(BatteryStatsImpl.java:8002)
at com.android.server.am.BatteryStatsService.updateExternalStats(BatteryStatsService.java:1366)
at com.android.server.am.BatteryStatsService$BatteryStatsHandler.handleMessage(BatteryStatsService.java:125)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.os.HandlerThread.run(HandlerThread.java:61)
at com.android.server.ServiceThread.run(ServiceThread.java:46)
Caused by: android.system.ErrnoException: open failed: ENOENT (No such file or directory)
at libcore.io.Posix.open(Native Method)
at libcore.io.BlockGuardOs.open(BlockGuardOs.java:186)
at libcore.io.IoBridge.open(IoBridge.java:438)
at java.io.FileInputStream.<init>(FileInputStream.java:76)
at java.io.FileInputStream.<init>(FileInputStream.java:103)
at java.io.FileReader.<init>(FileReader.java:66)
at com.android.internal.os.KernelCpuSpeedReader.readDelta(KernelCpuSpeedReader.java:49)
at com.android.internal.os.BatteryStatsImpl.updateCpuTimeLocked(BatteryStatsImpl.java:8002)
at com.android.server.am.BatteryStatsService.updateExternalStats(BatteryStatsService.java:1366)
at com.android.server.am.BatteryStatsService$BatteryStatsHandler.handleMessage(BatteryStatsService.java:125)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.os.HandlerThread.run(HandlerThread.java:61)
at com.android.server.ServiceThread.run(ServiceThread.java:46)
03-18 21:21:01.380 1363-1379/system_process E/KernelUidCpuTimeReader: Failed to read uid_cputime
java.io.FileNotFoundException: /proc/uid_cputime/show_uid_stat: open failed: ENOENT (No such file or directory)
at libcore.io.IoBridge.open(IoBridge.java:452)
at java.io.FileInputStream.<init>(FileInputStream.java:76)
at java.io.FileInputStream.<init>(FileInputStream.java:103)
at java.io.FileReader.<init>(FileReader.java:66)
at com.android.internal.os.KernelUidCpuTimeReader.readDelta(KernelUidCpuTimeReader.java:71)
at com.android.internal.os.BatteryStatsImpl.updateCpuTimeLocked(BatteryStatsImpl.java:8031)
at com.android.server.am.BatteryStatsService.updateExternalStats(BatteryStatsService.java:1366)
at com.android.server.am.BatteryStatsService$BatteryStatsHandler.handleMessage(BatteryStatsService.java:125)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.os.HandlerThread.run(HandlerThread.java:61)
at com.android.server.ServiceThread.run(ServiceThread.java:46)
Caused by: android.system.ErrnoException: open failed: ENOENT (No such file or directory)
at libcore.io.Posix.open(Native Method)
at libcore.io.BlockGuardOs.open(BlockGuardOs.java:186)
at libcore.io.IoBridge.open(IoBridge.java:438)
at java.io.FileInputStream.<init>(FileInputStream.java:76)
at java.io.FileInputStream.<init>(FileInputStream.java:103)
at java.io.FileReader.<init>(FileReader.java:66)
at com.android.internal.os.KernelUidCpuTimeReader.readDelta(KernelUidCpuTimeReader.java:71)
at com.android.internal.os.BatteryStatsImpl.updateCpuTimeLocked(BatteryStatsImpl.java:8031)
at com.android.server.am.BatteryStatsService.updateExternalStats(BatteryStatsService.java:1366)
at com.android.server.am.BatteryStatsService$BatteryStatsHandler.handleMessage(BatteryStatsService.java:125)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.os.HandlerThread.run(HandlerThread.java:61)
at com.android.server.ServiceThread.run(ServiceThread.java:46)
03-18 21:21:01.380 1363-1379/system_process E/KernelWakelockReader: neither /proc/wakelocks nor /d/wakeup_sources exists
03-18 21:21:01.380 1363-1379/system_process W/BatteryStatsImpl: Couldn't get kernel wake lock stats
03-18 21:22:00.040 1363-1377/system_process I/ProcessStatsService: Prepared write state in 10ms
03-18 21:22:28.020 2299-29937/com.google.android.gms I/EventLogService: Aggregate from 1458334342680 (log), 1458334342680 (data)
Alguém sabe o que está faltando para resolver???