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

- Restructured a number of MissionItem properties as well

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