NetStats: Add net stats to system bar.

PS2:
PS3:
Hide net stats view when notification area is disabled.

Change-Id: Ib35dd46b026dab00abe73966105806c54266e466

Conflicts:

	packages/SystemUI/res/layout/system_bar_notification_area.xml
	packages/SystemUI/res/values/vendor_styles.xml
	packages/SystemUI/src/com/android/systemui/statusbar/tablet/TabletStatusBar.java