Kill App on Long-Press Back Key (framework)

Change-Id: Ib78fff9e32d95a0a112ddd9274b79b3a3aa626b9

Conflicts:
	core/java/android/provider/Settings.java
	policy/src/com/android/internal/policy/impl/PhoneWindowManager.java
Enable long bress to kill by default
Added toast message to long-press to kill

Conflicts:
	core/res/res/values/strings.xml
	policy/src/com/android/internal/policy/impl/PhoneWindowManager.java