StatusBar: Add support to show data and wifi activities.

-- Show data activity icons.
-- Show wifi activity icons.

Conflicts:
	packages/SystemUI/src/com/android/systemui/statusbar/SignalClusterView.java
	packages/SystemUI/src/com/android/systemui/statusbar/policy/NetworkControllerImpl.java

Change-Id: Iee5038b007e91deeb2d3cb838ce3908818aefc91