Hardware key custom rebinding (1/2)

Framework changes to allow rebinding of the actions performed on the
following key press events: Home long-press, home double-tap, menu press,
menu long-press, search press, search long-press, app-switch press and
app-switch long-press.

The available actions are: Nothing, open/close menu, recent apps
switcher, search assistant, voice search, in-app search, device sleep,
and launch camera.

Change-Id: I72c0d220a09d79230bfa299e0521ed693e5c25f1

Conflicts:
	core/java/android/provider/Settings.java
	core/res/res/values/symbols.xml