PathFollower: 1) Added alarm in case of missing UAVOs
2) Cleaned up callback code.
HiTL: Code cleanups.
[HiTL]: Added update frequency displays to HiTL widget.

Conflicts:
	ground/gcs/src/plugins/hitl/simulator.cpp
Created MapArc class and made waypointcurve a child class.

Conflicts:
	ground/gcs/src/plugins/opmap/modelmapproxy.h
Renamed FlightDataModel class to WaypointDataModel class. This
creates namespace for the PathSegmentDataModel class.
Added path segment descriptor to flight data model.
[Map]: Add new map location icon.
[Map]: Renamed ModelMapProxy to WayPointModelMap proxy in order to make
namespace for the path segment descriptor model.
MapControl: Remove unnecessary class variable.
Map: Add path segment endpoint item class.
Map: WIP: Add PathSegementModelMapProxy. Still need to clean up a lot of
functions that were copy-pasted from WayPointModelMapProxy.
Map: Add support for PathSegmentDescriptor visualization.
Map: Fixed space formatting and changed two public slots to be private.
Map: Re-enumarated the GraphicItemTypes, and standardized the declaration
so that it will be easy to assign new numbers in the future.
Map: Fix arrowheads to always be in the right place and point the right
direction.
PathPlanner: 1) Fixed altitude bug in waypoint model
2) Ensured that longitude/east updates when north/latitude is changed.
PathPlanner: Added refresh timer to prevent flooding of the graphics
system. At 40 waypoints and 80 path segments, GCS would stall and crash due
to the load. Now it handles all points in less than one second.