Introduce z clipping of Polyhedron
Each method has its own commit, symmetry gets enabled in the last commit.
The idea behind the current implementation of z_clip is merge all faces below the clip plane into the edges on the clip plane by dissolving their edges onto the plane, if there is not any edge left which can be dissolved: merge the left over faces.
For each necessary Euler operation do:
- Poll geometric structures (e.g edges, faces) with specific properties from the polyhedron as long such are available.
- Do the operation on it.