Custom lockscreen

This commit Re-committed by @Namja in Triangles

Accessible via launcher wallpaper selector and
Settings - Display - Wallpaper - Lock screen

Change-Id: I2e4722d1a6d4ba80a3c656306ceb251d630a8e21

Conflicts:
	packages/Keyguard/src/com/android/keyguard/KeyguardViewManager.java
	packages/WallpaperCropper/AndroidManifest.xml