rename -> Face, Edge without prefix "Polyhedral"

• rename PolyhedralFace -> Face
• rename PolyhedralEdge -> Edge
• rename PolyhedralTopology -> Topology
• rename PolygonalTopology -> FacialTopology

(they were moved into namespace ff when this became a separate library; since then, the prefix "Polyhedral" is obsolete as there is no more risk of confusion with other faces or edges)

• split file pair PolyhedralComponents.h|cpp into Face.* and Edge.*