mods for doc build

[fs446]

I updated the sphinx doc build handling since the old handling did not work with recent package versions, at least not on my computer. I also added bib-file handling.

The conf.py file mods originate from taking and adapting the conf.py file from the sfs toolbox project, I am not an expert in this, so please check carefully.

I used a python environment that was created by conda 4.9.2 and conda create -n mysfa python=3.7.9 numpy=1.19.5 matplotlib=3.3.3 scipy=1.6.0 nbsphinx=0.8.1 sphinxcontrib-bibtex=2.1.4

[mgeier]

The conf.py file mods originate from taking and adapting the conf.py file from the sfs toolbox project

The SFS configuration is quite outdated and could need a facelift itself ...