deposit: fixes to fillform arXiv import

* Updates fields regarding the new OAI2 import API.

* Imports arXiv comments field onto note hidden field.

* Adds license url field if it's present in arXiv import.

* Strips created field imported from arXiv and year field imported from
  Crossref to Journal Information's YYYY year form field.

Signed-off-by: Pedro Gaudêncio <pedro.gaudencio@cern.ch>
deposit: arXiv/DOI priority change

Signed-off-by: Javier Martin Montull <javier.martin.montull@cern.ch>
config: ARXIV_API_URL removal

Signed-off-by: Javier Martin Montull <javier.martin.montull@cern.ch>