Remove unused code

The X-UAV Mini Talon is a V-Tail plane. This commit adds the
new group "Plane V-Tail" together with a svg image for the
new group.

Fixed the core MAVLink receiver. Among other things, it wasn't accounting for fragmented messages.
Fixed code that monitors messages received (and lost)
Added a section within the MAVLink panel to show the current status (for the current vehicle)
Remove some old, unused exposed interfaces

Also fixing some c++ errors within commented off code as the localization engine was getting confused by it.

Limit all queries to areas smaller than 500km^2. If an area of interest is greater, clip to 500km^2 centered on current ROI's center.
Removed the identifier "Airmap" from error messages coming from Airmap.
Added a clipping function to QGCGeoBoundingCube (clip polygon to given area)

Fixes https://github.com/mavlink/qgroundcontrol/issues/6770

I have no idea how this was building elsewhere at all.

Expose root plan keys

Replacing colors with the ones provided by Airmap.
Adding border color and width.
Adding airspace ID so it can later be linked to the advisory list.

Also cleaning up annoying c++14 warnings.

Fix swapped climb/descent

Fix incorrect qCWarning

Renamed "Invalid" (airspace) to "custom"

Hack fix for terrain crash when new query comes through before old query is complete

Don't show compass orientations for fixed orientation vehicles.