- Fixed found bugs in MissionManager

- Fixed bugs found to unit test

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

- fix bugs found by test
- Implemented Mock mission item protocol in

Also:
- Remove unused code

Plus lots of other cleanup

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

This is needed for Android since it needs to communicate with java apis
which require everything on the main thread. The additional thread was
not really needed since you can implement using a signal based approach
which ends up being the same thing.