Settings: More options added to hardware key rebinding (2/2)

In the same vein as the available Navbar actions, this adds the following new hardware key rebind options:
 * Last app: Switches to the last app
 * Power button: Turns off the screen
 * Custom app: Launches an application/activity of your choice

Change-Id: I3d9b0e447862a40a90ded22d3952cab09c9a48ab

Conflicts:
	res/values/arrays.xml
	res/values/strings.xml
Settings: Add Home/Back buttons available for rebinding (2/2)

This also removes the Kill App Longpress Back toggle in Development Settings since it is now a bindable action.
Preview of settings: http://goo.gl/uvrjF

Patchsets:
- rebase

Change-Id: Ief2f827e29ece715dc7a58b0997f1fbee89a4208

Conflicts:
	res/values/arrays.xml
	res/values/strings.xml
	res/xml/development_prefs.xml
	src/com/android/settings/DevelopmentSettings.java
	src/com/android/settings/slim/UserInterface.java