Improve bibliography

[gisellemnr]

At the moment, some bibliography files are added with the "addbibresource" command while others use "addsectionbib". We should make this uniform.

From personal communication with Bruno:

Yes, we should make this uniform... The differences between the two commands are explained here: http://texdoc.net/texmf-dist/doc/latex/biblatex/biblatex.pdf

Ideally, we should try to get rid of the need for "bibliographies.sty" entirely, by improving our "command.sty" file (look for "\begin{refsection}" and "\end{refsection}" there). I remember I had some technical difficulties, and that is why I ended up creating "bibliographies.sty".