Code review comment for lp://staging/~ctjacobs-multiphase/fluidity/compressible-multiphase

The code now includes the p*div(u) term based on the compressible logical only. The include_pressure_term option has been removed.

Regarding the diffusion term, the idea was for the user to give k/Cv in the .flml file. I've now removed the unused k and Cv variables, since k/Cv will be supplied in the 'diffusivity' tensor.