elsevier_package: CONSYN fixes

* Adds 710__g field for collaborations.

* Adds pagecount and article topics.

* Adds 260__t:published field.

* Removes 773__n field.
Signed-off-by:Georgios Papoutsakis<georgios.papoutsakis@cern.ch>
Merge pull request #33 from GiorgosPa/elsevier

elsevier_package: CONSYN fixes