mdwarf_hydro does not conserve angular momentum

[bpbrown]

The mdwarf_hydro.py anelastic script appears to not conserve angular momentum at present. This is a known issue from previous implementations, but we're just seeing firm evidence now. Suspicions of this arose from odd large-scale zonal flows being driven before nonlinear saturation. Inclusion of an Lz diagnostic appears to confirm this concern.

Task list:

• translate formed ell=1 boundary condition to d3 form
• implement boundary condition for ell=1