[3/3] settings: volume wake

Added new buttons category
This is a top-level category cause there will
be more things to come which we want to add here

PS4:
whitespace cleanup

PS7:
make adding button options device specific
add config_device_has_button_settings to overlay
to enable

Change-Id: I52f70d1632e7eb9088e5ff05f8d40e6876eff00e
Merge "[3/3] settings: volume wake" into android-4.3