Merge Navigation Bar and Pie Controls button config (2/2)

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 frameworks/base.

This commit introduces here:
* Some setting constants changes.
* Removal of the pie search key setting.
* Move pie controls to navigation bar settings

Change-Id: I5b4abd6d32a3fc835466ac4cb1f0b9c851641061

Conflicts:
	res/values/strings.xml
	res/xml/pie_control.xml
	res/xml/system_settings.xml
	src/com/android/settings/saber/PieControl.java

Signed-off-by: Paul Beeler <sparksco@gmail.com>