Liza Daly reported that the dc:identifer-generation code was garbage (she was right).

Liza Daly reported that the dc:identifer-generation code was garbage (she was right).

Added new tests:
- should include at least one dc:identifier
- should include an ISBN as URN for dc:identifier if an ISBN was in the metadata
- should include an ISSN as URN for dc:identifier if an ISSN was in the metadata
- should include an biblioid as a dc:identifier if an biblioid was in the metadata
- should include a URN for a biblioid with @class attribute as a dc:identifier if an biblioid was in the metadata