Add Center Clock-Framework Part

Patch Set 5: Rebase
Patch Set 6: Rebase and changed copyright message
Patch Set 7: Rebase and added null check

Change-Id: I80cfef86d556a468925ec22f42dd1638f7c90565

Conflicts:
	packages/SystemUI/res/layout/status_bar.xml
	packages/SystemUI/res/layout/status_bar_expanded_header.xml
	packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java
	packages/SystemUI/src/com/android/systemui/statusbar/policy/Clock.java
	packages/SystemUI/src/com/android/systemui/statusbar/tablet/TabletStatusBar.java