fixes #554

although it just sets it to the media_creator_username to their supplied name- if you want their username in the system (if they are logged in) that is already stored in the user_id field
added user_id to admin interface

fixes #553
added media_date_created to form POST

I added these fields to the submission forms and updated the existing items in the database. Although, judging from the amount of them (close to 3k) I believe molly is not adding them on batch import. fixes #530