... from assembleWithJacobian() into a separate method.
I added some constitutive data structs and reused some from TRM.

With that change, Process.h does not include the reflection code
transitively anymore, meaning less code dependencies and (hopefully)
better/more fine-grained incremental builds, since many other
compilation units depend on Process.h.

The original implementation in the assembleWithJacobian sneaked in erroneously.

Though the dmxWL/dpLR is possible, but through the code only primary variables derivatives are used, p_GR and p_cap.

This reduces number of Eigen's template instantiations and also
significantly helps with the runtime performance.

This simplifies some calls and avoids two recomputations
of the same quantity.

... for hopefully faster compilation.

This requires separation of enthalpies into FluidEnthalpyData
and SolidEnthalpyData, hence the many changes.

For pressures, gradients, and strain use only strong typed
values.