Bring material model from freesurface branch
Add tests
Documentation dump
Add testing output
Attempt to shut up clang
Update changelog
One more try to get rid of warnings
Clarify wording
Work on language
Change case of enumerations
Add units
Change name of ViscosityAveraging to viscosity_averaging
add note
Change case of parameters
Remove TODO
Simplify compute_volume_fractions
Simplify parsing of parameter file
Add more info with assert error
Clarify text
Restore messed up test output