Modified Route airspace to throw an unsupported-operation exception for addLeg and setLegs. See MDA-66. Added class documentation to Route and TrackAirspace. Added missing message property to TrackAirspace.

git-svn-id: http://worldwind31.arc.nasa.gov/svn/trunk@2424 822214bb-dcf7-4c8d-a767-17ae0fb20d88