Fix Polyhedron::is_inside only using relative location

Polyhedron::is_inside is using the vertices of face right now, which are just relative coordinates from the center of mass. Recently it was introduced that a Polyhedron can be initialized at a location other than the origin. Which results in no matter where the Polyhedron is located, the vertices that will be marked as "inside" by Polyhedron::is_inside are still located relative to the origin