Several bugs found and fixed surrounding Bezier Describe (track and line)
1. Using endpoints for non-track
2. Not altering angles when end points or control points altered
3. Wrong type of angle results for altering track ctl points when end tracks
4. Not clearing old track when updating
5. Not making endpoint 1 R/O when end track at that end
6. Bonus - angles a0 and a1 were not set up properly on creation of track/line
