Add support for writing 14-node pyramid elements to Exodus files.

This is pretty trivial, because Exodus doesn't really care how many
nodes a given type of element has... you just have to tell it.

Paraview, on the other hand, does not seem to be capable of displaying
these elements properly... if Paraview does display 13-node pyramids
properly, maybe a workaround would be to display 14-node pyramids by
omitting a single point?