M7.21 Add metadata to cover origin of bibliographies

Metadata and processing code added to RefBank to cover origin of bibliographies.

Use cases:
1) Bibliographies taken from a publication, in which case the origin is the bibliographic details of the original publication or (possibly) RefBank ID of original publication, which will be accurate but not human-user friendly.
2) Bibliographies contributed by a particular author, in which case, attribution of the bibliography is appropriate.
3) Bibliographies harvested from, or contributed by, existing resources such as ITIS, in which case the contributor is the short name of the existing bibliographic resource.

These ideas of origin could also be extended to attribute contributions made by people editing a reference.

This milestone was defined in M7.15.