mod_muc_bot: Save occupant to room This has some side-effects: Firstly, the bot shows up in occupant list, which is nice. Secondly, the bot starts receiving messages from the room which might be wanted, but it would be better to join the room for real in this case.

This module blocks configured queries that change server state.

E.g. to make vCard storage read-only:

``` lua
readonly_stores = {
	vcard = { "vcard-temp", "vCard" };
}
```