Active display: Allow apps to be excluded from being displayed [1/2]

This has been a highly requested feature so I guess it's about time
we implement it :).

Change-Id: I5c334833b78325733ae076c07afccebb02758ead

Conflicts:
	core/java/android/provider/Settings.java
	packages/SystemUI/src/com/android/systemui/statusbar/policy/activedisplay/ActiveDisplayView.java