BibFormat: fix issue in DataCite XSL

* Fixes an issue where an empty relatedIdentifiers tag was added
  causing DOI registration with DataCite to fail.
BibField: fix embargo & related identifier issue

* Fixes an issue with generating 942__l tags instead of 942__a tags
  for the embargo date.

* Fixes an issue with not parsing arXiv identifiers in the related
  identifiers field.
BibFormat: hide info title when body is empty

* Fixes an issue where the related identifiers info title would
  be shown, even though no related identifiers existed.
WebDeosit: fix issue in file sorting

* Fixes an issue with the comment used for sorting files.
WebDeposit: force identifier scheme detection

* Forces scheme decection of related identifiers.