Draft: Reversed the vertex intitialization order of Prisms

Put on hold. If this does not break any test, then tests are lacking.

By reversing the orientation of the faces, we reverse the face normal. Therefore the z-interval filled by our prism becomes (0,-H) instead of (0,H). If this does not break any test, then this means we only have tests of prisms in vacuum, no tests of prisms on a substrate.