More options added to hardware key rebinding (1/2)

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: I1ca98b1c615e4336c644d0247b4277b9421a96ff

Conflicts:
	policy/src/com/android/internal/policy/impl/PhoneWindowManager.java
Framework: Add Home/Back buttons available for rebinding (1/2)

Finally, we can disable or rebind all hardware buttons!
Also adds Expanded desktop toggle and Notification shade toggle

Change-Id: I0ca51c25e8434696a514fd1ef1e1e33543bf066a

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