Doxygen for 3.3
Todos:
* [x] empty doxyerr.log
* [x] check correct display of the equations
* [x] correct linking of the sites (see sanitizelinks.sh for previous fixes)
* [x] does work on the dumux website as well?
* [x] does the documentation make sense? spot mistakenly made copy& paste?
* [x] does doc/doxygen/modules.txt match the folder structure?, check for missing/wrong ingroup
* [x] fix copydocs used with forward declarations
For possible reference of a future doxygen dude:
The documentation is built by running make doc in the dumux build folder.
One way to switch doxygen versions is to:
* download the doxygen git repository from https://github.com/doxygen/doxygen.git
* checkout the branch you want, e.g. Release_1_8_17
* the first time do: mkdir build, cd build, cmake -G "Unix Makefiles" ..
* always do in the doxygen build directory: make, sudo make install
* the first time do: export PATH=/usr/local/bin/doxygen:$PATH
* delete the dumux build folder and rerun dunecontrol for dumux ./dune-common/bin/dunecontrol --opts=./dumux/cmake.opts --only=dumux all
issue