Moved WayPointCircle to MapCircle, since WayPointCircle is not specific to
waypoints.
Moved WaypointLine to MapLine.
Subclassed WayPointItem and HomeItem to new class MapPoint. This new class
will be used for geofencing and path segment descriptors.
Added enum for making QGraphicsItem type assignments.
Updated map functions to use physical_constants.h. Also fixed constant
usage in CoordinateConversions.c.
DistanceBetweenLatLng now returns meters, instead of kilometers.
Added DistanceBetweenLatLngAlt method.
Added MapPoint::DistanceToPoint_2D and MapPoint::DistanceToPoint_3D
methods.
Add UAVItem to MapPoint class.
Add GPSItem to MapPoint class.
Renamed class MapItem --> MapPointItem.
Moved type() to parent class.
Revert "Moved type() to parent class."

This reverts commit bea778afaa195959f116cbe2106efadbbb38708d.
Fixed copyright.
Fix compile-time warnings on OSX.
Fixed two lines of code that accidentally got taken out during
the GCS compile warnings cleanup.
Merge pull request #549 from kubark42/subclass-opmap-items

Subclass opmap items