Add more functionality to hardware key rebinding 1/2

new functions:
- make back key rebindable
- make home key short press rebindable
- kill target
- navigate home
- navigate back
- last app
- ime switcher
- power menu
- toggle the navigation bar

PS1,000,000: clean up some stuff and add the ability to disable individual keys

Change-Id: I5cb31572b3c57529327a302e3b286ca041e051bf