Various fixes, including diagonal jacobian transformations.

Feature/sumfact amatrix

Create Theta matrix for sumfactorization in constructor.  This is just a starting point for further implementations.

See merge request !37

Test cache behaviour



See merge request !35

Remove symbol (didn't rebase the first time)

I didn't rebase the first time so I missed some new symbols comming from nonlinear jacobian apply.

See merge request !33

Remove symbol



See merge request !32

Cleanup/use using

Use using instead of typedef.

See merge request !30

[bugfix] Fix generation of the notebook script after dune-python refactoring

Requires latest dune-python.

See merge request !31

Requires latest dune-python.

Feature/nonlinear matrix free

Depends on PDELab merge request https://gitlab.dune-project.org/pdelab/dune-pdelab/merge_requests/183.

* [x]  stationary CG
* [x] stationary DG

Important notes:

- The nonlinear_matrix_free_dg_numdiff throws a time out. I already reduced the grid size to 4x4 and I don't want to go any smaler. Maybe we just delete this test? I think it's ok if we only test numdiff in CG since we want to use symdiff anyway. Opinions?
- Instationary matrix free needs some changes in PDELab. Should be postponed until it is supported there.


Closes #26 .

See merge request !29

Feature/stokes symmetrization

This fixes #10 

See merge request !25

Make dune-perftool python3-compatible



See merge request !28