Add :projectID to DCTerms or BIBO

[kcoyle]

Project identifiers are issued by government and commercial entities and are increasingly included in scholarly work metadata.

Recommendation:

• This is a specific type of identifier and could be defined as a subproperty of dcterms:identifier. Add project to DCTerms. Alternatively, add this property to BIBO. BIBO uses dcterms:identifier, so a BIBO property could be defined as a subproperty of dcterms:identifier. (Note: to make this specifically an identifier, it may make sense to rename it: projectID.)