Making polygon simplification optional

This minor release makes the removal of collinear vertices in polygonize optional.
One situation in which retaining all vertices is useful is when checking whether the boundaries of two polygons intersect, which can be done by checking whether they share a vertex if collinear vertices are not eliminated.

Initial Release

This initial release is based on the algorithm implemented in PolyQR before release 1.2 (in which it will switch to PolyGrid).
Compared to that version, the SVG and TikZ output generation is generalized significantly and the tests cover some additional cases.