Too complicated supporting both modes as editor becomes more complex

These use OpenGL implementation which prevented moving to ANGLE
support. Since they are rarely used they are being remove instead of
being upgrade.

These use OpenGL implementation which prevented moving to ANGLE
support. Since they are rarely used they are being remove instead of
being upgrade.

- 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

Signed-off-by: kai <kai@uav-flightresearch.com>

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

- 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

Also restructured some toolbar positioning QML to handle resizing.