mod_delegation: added disco#items support disco#items are forwarded to managing entity when suitable. This feature is not yet in XEP-0355, but it should be added soon. "http://jabber.org/protocol/disco#items:*" is used as a pseudo-namespace to activate this delegation. Also changed spaces to tabs to follow Prosody coding style.

This module adds a command to `prosodyctl` for listing users.

``` sh
prosodyctl mod_listusers
```