OO-1741 remove ? from dummy avatar images, adding anonymous avatar and removing old avatar images outside the theme

OO-1739: backport the delete button in file element and use it in user profil for the avatar, in the resource description and in the catalog entry editor

OO-1733: clean up all possible references, the check to prevent deletion must happen before reaching the delete method of the service

OO-1732: take the number of user properties to render the first row of headers in the test archive file

no-jira: beautify the list of sub levels in the catalog if the number of levels is uneven and the view of type list