Renamed FlightDataModel class to WaypointDataModel class. This
creates namespace for the PathSegmentDataModel class.
[To be squashed]: Fixed define name.
Added path segment descriptor to flight data model.
Created MapArc class and made waypointcurve a child class.

Conflicts:
	ground/gcs/src/plugins/opmap/modelmapproxy.h
Fixed missing include.
Fixed HiTL breakage left over from control refactoring.
Correct bug which could arise when saving new flight modes
while using HiTL.
[HiTL]: Added update frequency displays to HiTL widget.

Conflicts:
	ground/gcs/src/plugins/hitl/simulator.cpp
WIP: Bleh.
WIP: A little happier. Now I have markers I can see!
Seeing lines now! But not seeing waypoint lines anymore. Kind of sad.
Fixed the missing waypoint lines.
Drawing works right, but still some issues with arrow.
Resolved more problems.

Still have problem with empty line, but currently resolved by
checking for it and canceling out. It's probably related more
to the filletting than the drawing.
WIP: Finally, the major and minor arcs are showing up correctly. I think
this is good enough to go back to working on the path planning code.
Changed marker.

Also removed the ability to drag path segment endpoints.

Still have a problem of clicking on them.
Fixed problem with path segment markers hanging around.
Whoops! Deleted too many markers.
Fixed last visualization problem. Now full circles are shown, too.
Remove unnecessary class variable.