Make Navigation Bar and Pie COntrols share the same button layout

Based on the commit series for pie controls, this commit
makes the Navigation Bar and Pie Controls share the same
button layout.
This commit applies the changes made in part 1 to the
Settings app. For the real commit see framework/base.

This commit introduces here:
* Some setting constants changes to avoid clashes with PA.
* Removal of the pie search key setting.