mod_ping_muc: Remove 'kick' status code The intent is "you fell off", not "you were kicked out", however older clients may not recognise the 333 code, but that will have to be an acceptable loss.

This module blocks configured queries that change server state.

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

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