Moves computation of Blin_coeff from the reference state setup to the linear solver setup
Moves the definitions of reference state structs outside of model files. This makes it possible to store a concrete struct (instead of a pointer) in Equations, similar to how the other members are treated. Aside from removing the need for ugly casting, this is beneficial for the upcoming anelastic solver, because it will need to know the reference state implementation.
This PR:
Blin_coefffrom the reference state setup to the linear solver setupEquations, similar to how the other members are treated. Aside from removing the need for ugly casting, this is beneficial for the upcoming anelastic solver, because it will need to know the reference state implementation.