Allows for signal count > 1

Also merged MissionController and MissionEditorController into single
MissionController implementation

This is in preparation for full Qml main window

Was failing due to large log output from incorrectly named
MockLinkLogVerbose.

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

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

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

If Facts are referenced from FactPanelController, we need to reference
count the AutoPilotPlugin such that it doesn’t get destroyed until
after the FactPanelController is destroyed.

- Download working again
- Fixed lots of bad error handling