Implement polygon partition

[patrickschulz]

Some cells (such as the spiral inductor using arbitrary-angle paths) generate polygon with a lot of points, usually too much for some tools (GDS allows only shapes with less than 400 vertices, cadence virtuoso expects polygons to have less than 4000 points). Therefor these polygons have to be split. I started with a triangulation, but I would like to implement something better, a partition into m-gons where m is an appropriate number for the used interface.