Refactored PX4 radio config to work with both PX4 and APM

- 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

QGCUASParamManager and friends are replaced by FactSystem

More consistent with Qml usage pattern

If parameter version is too old, setup is not supported

- 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.

Plus a large number of other changes to allow for orderly shutdown of
objects without crashes or asserts. This is need for unit tests to
create/delete global state around every test.

Allows parameter access from QML among other things

- allow unit tests to use QGCApplication
- clear global singletons for each unit test run