Pie controls.

Based on the multiple navigation key bar patch, this commit adds
basic pie controls. The implementation is inspired
by Paranoid Android but is completely rewritten.
The aim was to get as little intersection with existing code as
possible and provide a farily easy interface to extent these
controls by new slices (inherited from PieSlice).

The pie controls are only active when expanded screen is turned on.

Based on this commit there is another one that adds more optimizations
for Phone UI to pie controls. And there is a seperate commit for
the settings app, too.

Conflicts:
	core/java/android/provider/Settings.java
	packages/SystemUI/res/values/dimens.xml
	packages/SystemUI/src/com/android/systemui/statusbar/BaseStatusBar.java