Remove a commented out token that is a left-over from previous commits.
Minor simpifications.
Bring material model from freesurface branch
Add tests
Documentation dump
Escape underscores so that they can be input into the latex manual without further change.
Escape underscores so that they can be input into the latex manual without further change.
Greatly extend the documentation of the 'simple' material model to explicitly say what it actually does.
Add testing output
Attempt to shut up clang
Update changelog
One more try to get rid of warnings
Undo two parts of previous changes since there is apparently a script
(update_parameters.sh) that does these transformations automatically.
Merge pull request #21 from bangerth/fixes

Document the simple material model (and other related and assorted fixes).
Clarify wording
Work on language
Change case of enumerations
Add units
Change name of ViscosityAveraging to viscosity_averaging
add note