device: input: do not show option to force navigation bar if existing

if the device has navigation bars by default, do not show the force option.

also handle the case, if we forced navigation bars.
because if we force them, it hides the settings to unforce them ;)

Change-Id: I6c0d3cea968efdae1504e70599ed23b3e5aa756a
DeviceControl: add support section in preferences together with a help dialog

dummy entries ftw

Change-Id: Ib3f920c9d86eff804ca96249be8909df01353345