Fix: can_* and is_* properties were not dynamic. Added "files" property.

The following properties would only reflect the status at the time the file_area object was initialized:
    - can_access
    - can_upload
    - can_download
    - is_operator
    - is_exempt

 ... so if changes were made the user while online, for example, these property values would *not* also change to reflect the current state.

The lib[] and lib_list[] 'can_access' properties still have this flaw.

Also: Add a new "files" property to the dir[] and dir_list[] objects to report the current number of files in each directory database.