Add on-the-spot user preference dialog

Credit: PA
Custom lockscreen wallpaper [1/2]

Conflicts:
	packages/Keyguard/src/com/android/keyguard/KeyguardViewMediator.java

Conflicts:
	packages/Keyguard/src/com/android/keyguard/KeyguardViewManager.java
	services/java/com/android/server/power/DisplayPowerController.java