- 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

- 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

I didn't realize TC for Ubuntu had GStreamer installed.

Everything is now based off of default font pixel size

Also check for writable settings in unit test runes