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
Oh I see.  The generated link is different.  Either way, this comment applies to #547, the current PR.  In this one, only Collections are relying on records/show_fields.  GenericFiles relies on generic_files/show_fields.  In #547, I'm trying to consolidate them.