Elsevier, JATS: important fixes & clean-up

* Changes JATS affiliation parsing (fix for comma separation).
* Fixes updating Elsevier records with new PDF/A file.
* Fixes sorting packages from Elsevier with name "CERNR".
* Refactores package extraction code.

Co-authored-by: Samuele Kaplun <samuele.kaplun@cern.ch>