General code clean-up
BREAKING CHANGE: Pruned cyclic Vector3Pathways, further clean up

- Cyclic had never been properly implemented, and they're just as doable
  by having an event handler for the arrival even of the path steering
  behavior.
- Removed redundant Points property, which was there just because on
  cyclic paths the point list was different than the original path list.
Better IPathway documentation
BREAKING CHANGE: Removed redundant Pathway

Likely any pathway can be done as a subclass of Vector3Pathway, making
its abstract base class redundant. Removed.  Keeping IPathway.
Marking sample behaviors as obsolete, chances are I'll remove them