deposit: arXiv extra mapping fields addition

* Adds extra fields from arXiv (same as in oaiharvest).

* 980__a: 'arXiv'.

* 65017__a: arXiv categories

* 65017__2: 'INSPIRE' and 'arXiv'.

* 269__c: preprint date from arXiv.

* 037__: 9:'arXiv', a: arXiv id, c: arXiv categories.

* 035__9: 'arXiv'.

* 530__b: 'arXiv'.

Signed-off-by: Pedro Gaudêncio <pedro.gaudencio@cern.ch>
deposit: wrong mapping on conference info

Signed-off-by: Pedro Gaudêncio <pedro.gaudencio@cern.ch>