Allow changing screen-off animation (1/2)

* Allow enabling/disabling screen-off animation
* Allow selection between fade & crt effects if the device allows it

Change-Id: If6bb9afd7a753e1df013e88f7f39cea94e8fe565

Conflicts:
	core/java/android/provider/Settings.java
	core/res/res/values/config.xml
	core/res/res/values/symbols.xml