QS: Add dock battery tile (2/2)

Add a dinamic tile for devices with dock battery

Requires http://review.cyanogenmod.org/#/c/33999

Patchset 2: Rebased

Change-Id: If6c49a5277899997717f5a3af8ed3ad5bbb30b67
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>