Instead us a Toolbox concept which hangs off of QGCApplication

Also merged MissionController and MissionEditorController into single
MissionController implementation

- 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.

Otherwise they end up referencing deleted Facts on link disconnect

QGCUASParamManager and friends are replaced by FactSystem

More consistent with Qml usage pattern

Also many LinkManager API changes to further isolate all link
management inside LinkManager.

- properties now hand off of main “autopilot” object in qml
- Added support for summary items through qml

This way you don’t need to know parameter set ahead of time.