Add support for high-order Gmsh prisms (orders 5+) and pyramids (orders 2+)
After the recently merged !679 (merged) which adds support for input/output of most of the Gmsh high-order elements, we still need to add support for higher order prisms (5+) and pyramids (1+). The former can be done now with a little work to work out the ordering of interior volumes. The latter is more complex and requires the implementation of pyramids at a nodal shape level, possibly following on from !660 (merged).