'ip_simple' mimetic inner product. Coincides with the results from
'computeMimeticIP' to (roughly) the order of round-off on a
non-trivial test case.
The calling interface is
BI = mex_ip_simple(G, rock)
and some latitude has been extended towards multiple data types in
the various G fields (e.g., G.cells.facePos may be an 'int32').
Additional clean-up and optimisation is likely.
- mim_ip_span_nullspace()
Constructs orthogonal basis for mimetic IP null space.
- mim_ip_linpress_exact()
Adds term to impose exactness for linear pressure fields.
Re-implement mim_ip_simple() in terms of these procedures.
