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

This can only come from the heartbeat

- 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 fixed case where UASMessageHandler reported errors but walking
list turned up no errors