Override default petsc4py error handler

We /really/ don't want PETSc errors to be silent, so install an error
handler that calls MPI_Abort if an error occurs.
Activate extruded interior facet integrals in parallel

Now that the sparsity is built correctly in MPI, we can remove the
restriction that interior facet integrals are not allowed on extruded
meshes.
Add parallel extruded 2D advection tests

This just takes the existing serial tests and runs them in parallel
too.  Tests interior facet integrals in parallel on extruded meshes.
Update assembly cache tests to PyOP2 changes
Merge pull request #369 from firedrakeproject/mat-zeros

* mat-zeros:
  Update assembly cache tests to PyOP2 changes
  Add parallel extruded 2D advection tests
  Activate extruded interior facet integrals in parallel
  Override default petsc4py error handler