Adds creator setter to the Dublin Core Datastream, refactors DC spec to test this and removes some silly tests.
Update simple setters for date/keywords to also work over the DC object.
Adds a kludgy way of assigning the type agnostic creator information required in the DC datastream.
Update nucollections to correctly set their own DC record on update and edit
Replace the personal_creators= and corporate_creators= methods in metadata assignment with a single method called creators=, which takes a hash containing first, last, and corporate names for creators.  Updates tests/views/controllers to work around this.
Merge pull request #74 from nu-lts/feature/better_dc_records

Feature/better dc records