Split PathLike, Trail, and Path into separate modules

[fryguybob]

(Imported from http://code.google.com/p/diagrams/issues/detail?id=51. Original issue from byor...@gmail.com on September 6, 2011, 09:03:59 PM UTC)

Currently they are all in Diagrams.Path, but it's gotten big enough that it really makes sense to split them out. In fact, perhaps we should have Diagrams.Path.Segment, Diagrams.Path.Trail, Diagrams.Path.Path, and Diagrams.Path.PathLike? This is not too hard in principle, but note that it also requires updating

• any modules that import them, including examples
• the diagrams manual, where it refers to the Diagrams.Path module

[byorgey]

Closed via @705a9b2889c92267300b33e53bb4e13be3d65c9c.