Simpler control design for better mobile display

Better handling of Flight Plan Complete comm lost scenarios

New Resume Mission sequence

Multi-Vehicle Start/Pause Fixes

If briefing evaluation returns no authorization, assume none is required. This is reflected in the UI as "Authorization Not Required".

* Added support for sat count to Sensors check control

* QGCCheckListItem -> PreFlightCheckButton
* CheckList -> PreFlightCheckList

Automated preflight checklist: Initial commit. Note that this requires an autopilot firmware that writes the respective health flags in the SYS_STATUS mavlink message