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

- Also added new adjustMavlinkMessage support

- New MissionManager
- Plumb MissionManager through MissionEditor
- Mission Editor supports get/set

Plus lots of other cleanup

- Moved all MavManager functionality to Vehicle
- Updated all code to use Vehicle instead of MavManager
- Removed MavManager

- MultiVehicleManager is a Qml friendly replacement for UASManager
- Vehicle is a replacement for both UAS and AutoPilotPlugin