FicksLaw/FouriersLaw for Facet Coupling

In the current status the user gets no error when using a compositional or non-isothermal model together with the facet coupling framework. However, it the respective laws are not implemented.

In !1245 (closed), these are introduced. But the issue with obtaining the effective laws used in the (dim-1)-dimanensional domain still needs to be resolved in a nice way. -> Solved in !1684 (merged) by putting effective laws into the volvars.