mod_cloud_notify: Cleanup code and drop support for prosody 0.9 This removes some legacy stuff that was needed for prosody 0.9 We now use util.stanza:find instead of our own patched version to be more mainstream The unneeded module unloading code was removed, too

This module blocks configured queries that change server state.

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

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