Add measures to core types.
Add support for top and bottom facet zero form integrals.
Add support for extruded exterior facet integrals.
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.
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; fix test
Top, bottom and exterior vertical facets pass. Un-xfailed tests.
add interior facet stress tests (steady advection); tidy existing tests