Status bar Auto-Hide [2/2]

Add an option to auto-hide status bar when there are no
notifications.

PS 2 : Reorder a bit

Change-Id: I93b637f9b3e1036522f77ca4b299d385052320e5

Conflicts:
	res/values/strings.xml
	res/xml/status_bar.xml
	src/com/android/settings/carbon/StatusBar.java