[2/2] Add an option to disable hardware keys

This requires that the device supports the KeyDisabler
HAF methods, and is available in the Buttons menu

Change-Id: I01bd83b312745b4a8aa3bde0cf5f02ea99a888cc
BootReceiver: restore Keydisabler value
Button settings

Added new button settings screen in device category.

-Hardware keys
-Navigation bar
-Pie Controls
-Power button option
-Volume button options
Settings.java: list button settings as a valid fragment