MetadataRecord#fields returns a HashWithIndifferentAccess.
Ticket #17: Add more info to contribution ore:Aggregation
Ticket #17: Add EDM as RDF conversion methods to attachment model.
Rely on autoloading for RDF module.
Ticket #17: Include links to attachments in contribution EDM.
Ticket #17: Represent dcterms:temporal as edm:TimeSpan.
Digest YAML of properties hash for edm:TimeSpan class URIs.
Ticket #17: Use EDM Agent, Place & TimeSpan classes.
Use proc in Array#reject argument for code readibility.
Ticket #17: Use edm:Concept class for applicable metadata fields.