Improve support for arbitrary contours in shaping application

[kennyweiss]

Our intersection-based shaping algorithm currently supports 2D contours as input. It then linearizes the contours and revolves each generated line segment around the axis or rotation.

The algorithm currently only supports collections of input contours where each Piece is monotonic with respect to the axis of rotation. E.g. a circle would have to be provided as two semi-circles (appropriately oriented).

This makes it difficult/complicated/awkward for users to specify shapes of interest to Klee.

We should extend this to support more general input. Our algorithm could then either directly support the more complicated shapes, or subdivide the geometry into Pieces with appropriate geometric conditions.