Also additional major Mission usability changes

- Fix: Version error message not being displayed
- Correct handling of APM and PX4 files with respect to home position
in first slot
- Emit newItemsFromVehicle signal so editor can fit map viewport on
load from vehicle

Hamburger: Delete, Delete All, Show all Values

Hamburger: Delete, Delete All, Show all Values

Both altitude and acceptance radius will track last value

Also merged MissionController and MissionEditorController into single
MissionController implementation