New VehicleLinkManager implementation

These are defined in PlanManager. Having them here as well causes lost
signaling.

Also fixed bug with ArduPilot guided waypoint write which would trash
existing mission.

This time to handle correctly updating plan/fly view when plan changes

Works around ArduPilot strangeness with empty missions end

Fixed a pile of bugs as well

Retry in all the right/possible places. Don’t freak out about things
coming in unknown sequences.

Plus new unit tests

Also merged MissionController and MissionEditorController into single
MissionController implementation

- Fixed bugs found to unit test

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

Also understand the concept of missions which cannot be edited

- New MissionManager
- Plumb MissionManager through MissionEditor
- Mission Editor supports get/set