Merged requested to merge feature/numeqvector into master
Adds a new class NumEqVector which deduces it's type from a given PrimaryVariables type. This should make the NumEqVector property obsolete.
Do we need a proper PrimaryVariables concept to restrict the type? Probably not for now. Deprecate property? -> Probably try it out for one or two cases and to the actual deprecation in a separate MR?