Draft: Vectorial exprtk function arguments

Allow access of deformation_gradient, mechanical_strain, stress, total_strain, and total_stress in the exprtk expressions of the MPL Function property.

Because, if I understood the details of exprtk implementation correctly, exprtk needs pointers to data upon construction, one implementation for 2D case and another one for 3D case is provided.

1. Feature description was added to the changelog
2. Tests covering your feature were added?
3. Any new feature or behaviour change was documented?