reorganize `documentation' menu

Motivation

I think these pages are confusing and it is still difficult to find information here - although the installation instruction have greatly improved!

As pointed out in #87 (closed) the beginners resources is a weird combination of different instructions which are really confusing and often point to resources hosted outside of duneproject.org and not modifiable by core users. I don't that is a very good idea. More then once I had users following one of those resources and I had to tell them to completely remove everything and start from scratch with some script I could provide them. Not a good start for new users. Nothing mentioned there works for my or Roberts preferred workflow - we could of course add our own scripts and instruction there. But as said before I don't think that is a good thing to do and just looks confusing especially for some Beginners Resources. One of the reasons why I went through these pages was, that I was trying to find a place to add the new pip installation option and really couldn't figure out a good place to do that.

Current structure:

Here is a summary of the current structure of this menu (I might have missed something):

• Installation: focusing on building dune from source
• Python bindings: how to activate the python bindings for source modules
• External Libraries: grid manager (Alberta, UG), IO (Gmsh) Other (psurface), istl (superlu, suitesparse)
• Grids: grid implementations and their features
• Cheat Sheet: a pdf which seems up to date
• Compilers: list of supported compilers
• Tutorials:
  • link to installation
  • build system,
  • parallel communication interface, virtual refienment, dune-istl tutorial (these link to the gitlab repo of dune-common/geometry)
  • link to dune-grid-howto
  • link to the view-concept
• Class documentation: doxygen docu for each release version
• Buildsystem
  • documentation: includes some 'further resources'
  • dune-fem Python bindings (shouldn't be here - don't even know how that got here)
  • testtools
  • sphinxes (empty link)
• Beginners Resources: some general introduction then
  • Oliver's book
  • Oliver's take on installation
  • Installation from source
  • Installation via source using a shell script: this is something from Peter focusing on dune-functions I think although the repo that one has to download contains a lot of PDELab folders
  • Additionally in a small paragraph links to installing dune-pdelab and dune-fem are included.
  • final entry is 'Computer Requirements'
• Guides:
  • copyable entities/intersection (for grid dev. on how to get rid of EntityPtr?)
  • bug reporting
  • repository layout
  • coding style
  • whitspace hook
  • git best practice

Suggestion for new structure

• Resources for new users
  • system requirements
  • installation from source
  • installation using packages (.deb or pip)
  • setting up a new dune module
  • further resources:
    • build system docu
    • cheat sheet
  • reporting bugs
• Resources for developers
  • coding style
  • build system docu
  • git repository layout (to include whitespacehooks and git best practice)
  • reporting bugs
• Grid managers
• Discretization modules
• Class Documentation

Remarks

• So far I haven't included anything from the 'beginners resources', 'external libraries', and 'tutorials' (except build system)
• Most of the entries above are already written. I would like to add the 'Python bindings' entry to 'installation from source' and the 'installation using packages' (better title required) needs to be written I think.
• We could add something like 'Further resources' where we could include the docu on 'virtual refinement' for example - but I would prefer a pdf and not a link to the tex file in the doc folder of dune-geometry.
• We could have an entry on 'installation instructions for further dune modules' which could then contain a link to Peter's repo of installer scripts, and Oliver's pdf, and similar scripts for dune-fem etc. But actually I think this is information that should be included with the modules in question? Remark: Robert added a Disc. module entry above were this could be included.