Add possibility to add ACL fpr authenticated users and return 404 for non existent entities
ACLs with the agent
predicate set to acl:AuthenticatedAgent
allow
every authenticated user to work with the linked object according to the
defined acl:mode
.
Also, while checking the ACLs, if the subject is not present in the repository, a 404 instead of a 403 HTTP status is sent back.
Related to #123 (closed), #127 (closed)