Dubins update

Added getters and setters for minimum turning radius
Changed DubinsLineObject to fix "false loops" in displayed flights

We fudge the min. turning radius number a little bit so that slight
floating point errors don't cause extra, unnecessary "dubins loops"
Fixed "false loop" issue for exporting flight solutions also
Fixed issue with bounding box of DubinsLine map object
A* intermediate granularity changed from 300->75 meters
Reorganized some files in WaypointPlanner
Modified WaypointMapView constructors

so that the default constructor doesn't require a scene
Added a method to Wayset to return "integral" waypoint distances
WaysetDisplayManager now emits signals on changes and selections
Added a horrible timeline widget to comparison interface