Remove Diffusion::visc_coef because it's not used in Diffusion.
Move checks on visc_coef from Diffusion to NavierStokes (which actually uses visc_coef).
Remove NavierStokesBase::Initialize_specific.
Minor clean up of NavierStokes Initialize for clarity and to quiet compiler warnings.
@esclapez I don't think any of this requires any changes in PeleLM. However, it will allow you to remove a superfluous visc_coef array which I think derived classes previously were required to carry.
Remove Diffusion::visc_coef because it's not used in Diffusion. Move checks on visc_coef from Diffusion to NavierStokes (which actually uses visc_coef). Remove NavierStokesBase::Initialize_specific. Minor clean up of NavierStokes Initialize for clarity and to quiet compiler warnings.