[2/2] illusion settings: add custom hardware button mapping

Possible mapping

 0 - Nothing
 1 - Menu
 2 - App-switch
 3 - Search
 4 - Voice search
 5 - In-app search
 6 - home
 7 - back
 8 - toggle last app
 9 - kill app

PS7: Fully working

Change-Id: I3b8b3bbd31b416d0952acd1f9a86cdd28a8002e5