In particular remove non-recommended installation command that also
contained an outdated --use-cmake option which doesn't exist anymore.

Change input parameter group name from SpatialParameters to SpatialParams as SpatialParams already exists while SpatialParameters would be lonely.

[doc] Correct Freeflow to FreeFlow for EnableUnsymmetrizedVelocityGradientForBeaversJoseph, because that is how it is spelled in the code also.

[doc] Remove \b in front of Grid and Newton, as Angular0/1/2 and EnableAbsoluteResidualCriterion won't be the first entries of their category any more in the next step.

[doc] Change the positions of ElectroChemistry.pO2Inlet, Grid.CellType and LoadSolution.PriVarNamesState to where they belong alphabetically.

[docu][doxygen] Change dot image format from png (default) to svg to reduce the size of the doxygen html folder to less than 40 percent.

We require Dune >= 2.7.