Modifications to plugins/browsing.

I wanted to have Select boxes for Owner and Group - also noticed that changes to Owner and Group weren't being save.

Changed inputs to readonly: Resource, Created, Last Modified.
Changed to Select: Owner, Group (live lists of available Users and Groups are loaded from the db as needed)
Added empty item to Access Control List (to overcome problem when no ACL is present)
Modified "Save" button action so that changes to Owner, Group and Mime are now also saved.