liblight: Add battery light support

Change-Id: I4b73363545b71fbb435b9b577fdfff30d756b90c

Conflicts:
	overlay/frameworks/base/core/res/res/values/config.xml
Sync with cm
hammerhead: Always keep 3 buffers ready

 * Reduces overall jank system-wide

Change-Id: I37f6021237c81197063d3fd1fd7e5e07626490c9
hammerhead: Better mount options to improve performance

Change-Id: I18f7165c2ff8547b7968d946336d948fe30522b1