Pass variables prev to MPL Property::value() calls.
Avoids misusing of current iteration values in variable_array for the previous time step values. Exemplary on the PorosityFromMassBalance but same will be needed for the solid material model calls requiring previous time step values for strain and stress.
Included a small cleanup on porosity naming in local context.
- Feature description was added to the changelog
- Tests covering your feature were added?
- Any new feature or behavior change was documented?