#2719: Move preview above title. Remove Gallery Titled field. Repurpose Gallery Description.
#2719: Replace preview image with link to file when it's not an image or video.
#2719: Add new description field of our own. Migrate media_description into it.
#2719: Properly add new field to file type.
#2719: renaming things
#2719: Correct update hooks for creation and migration of description.
#2719: Shrink size of description field
#2719: Use filename instead of media_title in gallery.
#2719: Migrate media_titles to filename for image gallery files
#2719: Put replace field below the preview.
#2719: Resolve merge conflicts with 3.x
Merge pull request #4136 from openscholar/2719-file_edit_form

Clean up File Edit form