Bring Doxygen up to date

I had a quick lock at Doxygen today.

The question that we should discuss is:

What do we (not) want to document in Doxygen?

Under Modules we currently have a list of available models and discretization schemes. This seems good to me and maybe could get a small update.

The newly established Multidomain simulations part should also be in there in my opinion.

We also list our Material/Fluid Framework, which looks good to me.

Then we have Benchmarks and Tests, which is not really a module in my opinion and could be replaced by our examples in the near future (3.1). So we could get rid of this.

And then there is Adaptive Assembly Common Input Output Linear Nonlinear Parallel

where I am not sure if we could combine them maybe.

We used to have a feature list and a parameter list. Do we want to have them also in 3.0? And if so, in which detail level? The last time I tried this, we opted more towards a general feature/parameter list without listing all the possible combinations and variations.

Comments?