Add "end cap angle" capability to "thick linestring" and Roads

[BudgieInWA]

From a discussion on intersection turns/movements, we talked about the idea of allowing roads to end with an angle other than 90 degrees.

The ability to generate thick linestring and "parallel" geometry with an arbitrary angle at the end will allow us to:

• have roads join intersections at differing angles,
• seamlessly join roads together at Connection type intersections.

[BudgieInWA]

The desired road/lane end angle (where the stop line is often found) is just like the line of reflection that would be found running through a miter, if the road continued along the grey markings. Perhaps these "angled end caps" should be implemented as a capability of our "thick line strings". Seen angStart and angEnd arguments in getParallel

[dabreegster]

The point projection does 90 degrees in the start/end, look at generalizing