Settings: reduce navbar observer footprint (2/2)

time for code cleanup projects. Switch to same
logic we already use in QS/NT shortcuts. Use
only one string for the whole navbar config
This reduces massive the observer footprint.

NavRing and SlimPie will follow with same logic

cheers

Change-Id: Ia9c31c0723f3c8c55391ad6e43b6fe3e98c7470b