- override by vehicle type
- override by firmware type

Instead us a Toolbox concept which hangs off of QGCApplication

- select active vehicle
- arm/disarm
- select flight mode

- Also added new adjustMavlinkMessage support

- FirmwarePlugin is the new place for code which is specific to
firmware flight stack
- FirmwarePlugin currently supports flight mode apis
- Modify code to use new FirmwarePlugin support