Add flight plan deletion

Moved flight planning away from "Flight Management" to its own class. Planning does not need a connected vehicle.

Plus various bug fixes from flight testing

Also remove custom gimbal support

And fixes they found

When downloading mission items from the autopilot we need to retry more
agressively, so use a shorter timeout. If we don't do this, we might not
re-request a mission item in time and the autopilot has already given up
the overall mission transfer.

This fixes the case where a mission request from QGC to autopilot or a
mission item from autopilot to QGC gets lost on the link and needs to be
requested again.

* Flight modes still not implemented. Waiting on message change.
* Also includes various cauterization of UI things which should not be
available on high latency link.

By adding a member variable for the total mission item count, we can
actually correctly estimate the progress.

Float comparison to flakey cross-platform

Break apart string of classes into their own files as all in one file became unwieldy
Expose Airspace data in a QML ready format
Split global Airspace from AirMap (Only now I figured out the reason for the pure virtual root classes)
Refactored a bunch of things to make it consistent and/or obvious

Move all airmap related stuff to its own directory