Only set the ModsResource subject if there is a modsIdentifier.

Otherwise, just treat it as a blank node. In the UMDM we have been experimenting with, this occurs in the related item records (relationships/relation in the UMDM). This prevents multiple, possibly distinct nodes from being conflated by all using the dummy URI provided in the original LOC XSLT.
Use the generated ID as a blank node ID.

For the MADS name resources, create as blank nodes using the XSLT-generated node id as the rdf:nodeID. This avoids "resource not found" errors when importing the RDF into Fedora 4.
Merge pull request #4 from peichman-umd/resource-uris

Resource URIs