BibFormat: various fixes

* Fixes the displaying of 773_x field twice

* Displays properly the texkey

Reviewed-by: Javier Martin Montull <javier.martin.montull@cern.ch>
BibFormat: display NTIS link

Reviewed-by: Javier Martin Montull <javier.martin.montull@cern.ch>
BibFormat: don't display collaboration twice

Reviewed-by: Javier Martin Montull <javier.martin.montull@cern.ch>
BibCheck: fix unicode issue in doi plugin
BibTasklet: new Tasklet to harvest from CONSYN

* Adds a new BibTasklet to harvest records and fulltext XML from
  Elsevier CONSYN service. It downloads updated record sets from
  an ATOM feed given as parameter and converts each record to
  MARCXML format using the new harvesting-kit package.

* Creates necessary folders if CFG_CONSYN_OUT_DIRECTORY does not
  exist in config.py.

Reviewed-by: Jan Aage Lavik <jan.age.lavik@cern.ch>
BibTasklet: some minor fixes to CONSYN

* Fixes os import.
* Adds harvesting-kit and BeautifulSoup to requirements.txt.
* Does some kwalitee related fixes.