solid thermo (heSolidThermo) initialisation of psi, mu

heSolidThermo does not initialise or update the psi,mu of the base class (rhoThermo). This shows up when calculating turbulence for multi-phase systems (e.g. icoReactingMultiPhaseInterFoam) when accessing divDevRhoReff.

The underlying problem is that the solid transportModels do not implement mu(), psi() functionality. See #856 (closed). The current solution is to explicitly set the mu, psi to 0 in the multi-phase system constructor.