1) 846 Bug fix - generate correct logic and code for the call to
enforce_bc_kernel after a call to matrix_vector_kernel. Also add
w2h and w2v as spaces that cause enforce_bc_kernel to be called in
addition to W1 and W2.
2) 853 Bug fix - make sure that an operator object is only used
as a lookup for values in the PSy layer when it is correct to do
so. In particular, make sure that the dofmap lookup is always from
a field, as this fixes the known bug.