Next attempt at getting the cell right.
turns out vectors are not scalars
missing subscript
Handle OuterProductElements
now with extra testing goodness
Merge pull request #404 from firedrakeproject/manifold_cell_again

* manifold_cell_again:
  now with extra testing goodness
  Handle OuterProductElements
  missing subscript
  turns out vectors are not scalars
  Next attempt at getting the cell right.