[Timob-17358]: Update Appcompat assets + scons

[hieupham007]

This PR contains the following changes:

Update scons to build with Android-21
Update appcompat libraries and assets to run with Android-21
Update android projects to run with Android-21
Update theme.xml
Fix a crashing issue with the new libraries
Refactor Notification
Add Support for Material Theme
Implement category, priority, visibility properties for notification

[pingwang2011]

KS does not work. Only black screen shows.

[pingwang2011]

The very first comment needs to be addressed. Need to add a null check for iconUrl.

[pingwang2011]

Functionally tested (used build tool 21.1.0):

1. Ran KS. Worked fine on 4.0 device. But failed installing on 5.0 emulator with the error message:
   W/PackageManager( 339): Package couldn't be installed in /data/app/com.appcelerator.kitchensink-1
   W/PackageManager( 339): com.android.server.pm.PackageManagerException: Package com.appcelerator.kitchensink requires unavailable shared library com.google.android.maps; failing!
   W/PackageManager( 339): at com.android.server.pm.PackageManagerService.updateSharedLibrariesLPw(PackageManagerService.java:4965)
   W/PackageManager( 339): at com.android.server.pm.PackageManagerService.scanPackageDirtyLI(PackageManagerService.java:5271)
   W/PackageManager( 339): at com.android.server.pm.PackageManagerService.scanPackageLI(PackageManagerService.java:5057)
   W/PackageManager( 339): at com.android.server.pm.PackageManagerService.installNewPackageLI(PackageManagerService.java:9881)
   W/PackageManager( 339): at com.android.server.pm.PackageManagerService.installPackageLI(PackageManagerService.java:10389)
   W/PackageManager( 339): at com.android.server.pm.PackageManagerService.access$2300(PackageManagerService.java:230)
   W/PackageManager( 339): at com.android.server.pm.PackageManagerService$6.run(PackageManagerService.java:8335)
   W/PackageManager( 339): at android.os.Handler.handleCallback(Handler.java:739)
   W/PackageManager( 339): at android.os.Handler.dispatchMessage(Handler.java:95)
   W/PackageManager( 339): at android.os.Looper.loop(Looper.java:135)
   W/PackageManager( 339): at android.os.HandlerThread.run(HandlerThread.java:61)
   W/PackageManager( 339): at com.android.server.ServiceThread.run(ServiceThread.java:46)
2. Ran a test app with material theme by setting targetSDK=21. Worked fine on 5.0 emulator.
3. Ran KS->Phone->Notifications. Worked fine.
4. Need a more comprehensive test case for notification to test for both regressions and new features.

[pingwang2011]

CR + FR passed. Will merge after updating the doc.

[pingwang2011]

Doc reviewed. Accepted