Adds full metadata editing for Collections (same DC fields as GenericFiles)

Fixes hydra-editor style partials in views/records.

refs gwu-libraries/gw-sufia#82
refs gwu-libraries/gw-sufia#25
I'm going to open another non-blocking PR that makes app/views/generic_files rely on records/edit_fields instead of separate generic_files/edit_fields.  Can I address this itemtype issue there so that the current PR can go through?