mod_cloud_notify: Identify (and immediately push) urgent stanzas, e.g. calls This covers the following things: - A session that appears online, but has a broken TCP connection - Clients such as Siskin and Snikket iOS that require a push for calls to work It allows the stanza to be pushed immediately instead of waiting for the session to hibernate or an ack to timeout. It shouldn't break any existing cases.

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

``` sh
prosodyctl mod_listusers
```