Add support for top and bottom facet zero form integrals.
Add support for extruded exterior facet integrals.
Add another extruded facet test. Fix issue with exterior vertical facets.
Add horizontal facet integral with temporary fix for avoiding double jacobian kernels.
Attempt to add interior vertical facets.
Interior facet integrals for zero forms.
Split tests on extruded facets.
Solve a Poisson equation on exterior top and bottom domains.
layers -> layers - 1
Adding functionality tests (but not correctness tests)
Add changes to support the sparsity building for horizontal facets.
Top, bottom and exterior vertical facets pass. Un-xfailed tests.