noperts: Reproducible proofs of non-Rupert polyhedra

This features the newly-discovered “septopert”, a seven-vertex noperthedron, and a proof that this is the fewest vertices possible for a noperthedron.

Previously:

• Rupert’s property: cut a hole in a polyhedron big enough for an identical copy to slide through
• Rupert's Snub Cube and other Math Holes