[doc] Remove section about outdated highlighting file

See merge request !511

Some links were outdated/not working.

[freeflow] Add files for estimating the properties of a turbulence flow

See merge request !463

Handbook/improvements for release

See merge request !411

Cleanup/fs 338 3pwateroil

Fixes #338 and #337.

See merge request !261

Feature/use adl for std functions

* `std::swap` and `dumux/common` was cleaned up
* much more needs to be done
* I found a bunch of other clean-up stuff

See merge request !259

The changing constitutive relations task in exercise 1 previously was about
exchanging the EffToAbsLaw with a LinearMaterial law. It makes more sense to
replace the RegularizedBrooksCorey.
The description in the handbook was adapted accordingly.

Fill missing entries in feature table

*Delete unused entries

Include new features, add links to models and test problems

Should even work when they stick to version 3.0, but
not vice versa.

Testing links for implicit models

*Fix errors
*Add .bib entry for citation

* Reduce number of template arguments
* Rename property from tau to TauTortuosity

Reviewed by heck

Instead of calculating it in the local residual, the effective permeability
is now calculated within a new file permeabilityrutqvisttsang.hh in the
folder dumux/material/fluidmatrixinteractions.
This is just one possible effective permeability model. Several others can be
added and set via the property EffectivePermeabilityModel.

Up to now, the permeabilities were averaged twice, first by calculating
the mean of the mean of the intrinsic permeabilities in the flux variables
and later by averaging the effective permeabilities in the local residual.
This is redundant. Now, only the mean of the effective permeability is
calculated in the local residual.
This change required to change the reference files for the sequential and
the parallel test.

* in handbook and doxygen
* add hint in the opts file

Handbook:
- don't use deprecated Latex commands \it and \bf
- use the \Cplusplus macro consistently

Doxygen:
- put FluidStates group to the right hierarchy level
- improve wording

*Use headlines to separate the individual sub-models
*Remove \copydetails Dumux::TwoPTwoCNIModel as this no longer
 exists