Hideable battery icon

PS2: Create ContentObserver in BatteryMeterView and utilize it's onAttached/onDetached
PS3: Remove .save's

Change-Id: Ic14dd1c12220a447364a82ba258e9fdac8eb017b
Signed-off-by: kecinzer <kecinzer@gmail.com>

Conflicts:
	core/java/android/provider/Settings.java