Previous order was signalling new mission items available prior to in
progress going false. This was causing MissionController to pull an
empty mission list.

Instead us a Toolbox concept which hangs off of QGCApplication

Also merged MissionController and MissionEditorController into single
MissionController implementation

- Fixed found bugs in MissionManager

- 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