Switch to vertex data evaluation on system tests
The following discussion from !128 (merged) should be addressed:
This requires an update of all system tests. The Python scripts only work with cell data. This is the only reason why
vertexDatais not set to
I have a Python implementation ready which can also evaluate vertex VTKs, based on Oles
dune-vtkdiff, see https://ts-gitlab.iup.uni-heidelberg.de/dorie/dorie/snippets/16. I'll probably use that to update the Python test evaluators "soon"_
How to test the implementation?