Literature updating: get_biblatex.py to use read_bibfile (dict) for handling bibfile and bibitems

[keelinm]

The get_biblatex.py code currently accepts the bibfile as a string and returns new bibitems as string. For the flow of the code when updating the bib file automatically it would be smoother if it would make use of the read_bibfile method from processbib.py where the bibfile is given as a list of BibEntry objects which have keys and various fields.

[drepeeters]

I have created a new branch "dev_dre" in the Literature repo. Here, I have made some changes to at least make the get_biblatex.py code to accept the bibfile as a list of BibEntries instead of a string. @marinadamato I have tested this code but could you also test this during the next Literature update?

We still have to change how the new items are added to the .bib file as this still depends on a string format.