now I can choose to rotate either or both of harmonic / biharmonic viscosities / diffusivities. Also, enabled smagorinsky biharmonic over harmonic
updates to diagnostics to report VIS4 quantities when both VI2 adn VIS4 are enabled
Updated checkdefs to print 2/4 suffix to _MIX_ options so that the output files don't scare me.
Merge branch 'rotate_mixing'

It looks like rotating the mixing for the harmonic and biharmonic
viscosities separately is working well.