Fork navbar layout for quickstep

Different navbar layouts are loaded via config.xml depending
on if Quickstep is enabled. A contextual button frame is added
to replace the right nav buttons so different styling can be
applied. New back, rotate and keyboard icons are added.

Maintains support for custom navbar layouts. Adds support for
nested reversable elements, needed for contextual button frame.
Fixes navbar gravity support by using RelativeLayout's gravity
and top/bottom switching.

Change-Id: I5e24b2392c377313d421c0f95c3a7a0b99f32590
Fixes: 79930722
Fixes: 79930974
Fixes: 80164476
Test: manual, crash sysui, test against a11y, gb menu, rotate