Convert sigma_.. to vectorial sigma.
Update output prefix.
Move search length to top.

Add --reference PATH option to ogs, which when present
will execute tests (vtkdiff) constructed from the
<test_definiton> section in the project file.
This section contains the tester (vtkdiff for now)
the file, field, and absolute and relative tolerances.

This allows the user to run tests w/o cmake and includes
the previously separated test description into the
project file.

Make local source term definition possible

Use the specified patch mesh instead of the entire bulk mesh to define
the source term.

MateriаlIDs based solid models in phasefield processes

Same changes as in PhaseField process.

The multiple inheritance for the phase field extension
is not actually needed and can be completely avoided.

Use Solid Material Models from MFront

... such that one can copy and paste the vtkdiff commandline to the
terminal and immediately run it

Tutorial books contain links to the old OGS-5 keyword documentation.