Definition of circulinear shapes and some implementations.

Circulinear shapes are composed only of pieces of lines and circles: circle arcs, line segments, rays... They have many interests:

- their length can be computed easily (if they are bounded)
- they can be transformed using {@link math.geom2d.transform.CircleInversion2D#CircleInversion2D(Circle2D) circle inversion}
- they can be used to represent exactly (i.e. without polygonal approximation) the buffer of a circulinear shape.