SystemUI: Status bar clock - fixes

This commit fixes:

- no overlapping more from status bar icons on center clock.
  The width depending on what the user has setuped (date and clock) is exactly meassured now
- do not start animations if they are not needed
- reduce settings provider calls
- a bit cleanup

Change-Id: I7a37a6ae8f9bad0f265119af05dc20cf21cd6890

Conflicts:
	packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java
bootanimation: Only try to shutdown the mediaplayer if it was prepared

The bootanimation tries to shutdown the mediaplayer gracefully by waiting
on an asynchronous shutdown event for 5 seconds.

If, however, there is no boot sound, that asynchronous shutdown event will
never happen and the animation will be stopped for 5 seconds before shutting
down.

Visibly, this fixes the issue where the bootanimation would simply stop near
the end for exactly 5 seconds.

Change-Id: I77f5631368c7d9b9fef7941a6278af9c36032044
SystemUI: Ensure that the Clock is actually enabled in IconMerger

to device if we need to calculate

Change-Id: If12b0e26b32f044f1a82cf8b539283194d1d0b4c