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