Extend admin area information

[mzur]

Extend the admin area so admins can get a list of all storage requests (ordered either by total size or created date). Admins can click on a storage request and see the same view than the one for reviewing a request (without the action buttons) with thumbnails ( #4 ).

The challenge here is to implement tracking of file sizes. Currently there is no way to determine the total size of a storage request because the information is not stored in the DB. Either store the size of each individual file or just store the total size of all files of the request (both options must be kept in sync if files are added/removed).

This could even be used to improve the UX of a user when files, directories or requests are deleted, as we can now immediately update the UI showing the current use of the storage quota.

[mzur]

File sizes are now stored in the DB.