WIP: Add CircularArcIntersector

[dbaston]

This PR adds a CircularArcIntersector that computes intersections between
circular arcs and/or line segments. The intersections may be points or arcs.
The interface generally mimics that of the LineIntersector.

Missing features:

Use of a PrecisionModel
Handling of Z, M
isProper()
isInteriorIntersection()

A challenge I ran into when writing test cases is the lossy conversion between how arcs are stored (three points) and how we generally must work with them (a center point, radius, two angles). This can cause small differences in the computed center point, which currently prevents the code from recognizing the arcs as co-circular. It may be necessary to add some tolerance in the center-point equality testing, possibly by using the scale of a provided PrecisionModel.

[pramsey]

Is there a similar tolerance issue around arcs with infinite radius (aka straight lines (aka three control points in a line))?

[dbaston]

Is there a similar tolerance issue around arcs with infinite radius (aka straight lines (aka three control points in a line))?

Good point. See the final (failing) test added in 9910456.