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

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
Fix issue with hardware keys KEY ACTION comparisons.

Menu unlock now works properly.

Patchset 2: Switched detection of onscreen keyboard input to KeyCharacterMap.VIRTUAL_KEYBOARD

Change-Id: I092258fc20789a12123e319ed2dca25c55bb9f0c