Still a bit buggy

Plus many load/save fixes

- Load/Save working
- Entry point working

Plus new unit tests

It is also no longer a user visible field

# Conflicts:
#	src/MissionManager/MissionManagerTest.cc

Also additional major Mission usability changes

- override by vehicle type
- override by firmware type

- 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