mod_cloud_notify_encrypted: Use new 'util.crypto' on Prosody 13.0 This removes the dependency on lua-luaossl when running on Prosody 13.0 (or trunk) which has util.crypto Compatibility with Prosody 0.12 retained but also the dependency

This module blocks configured queries that change server state.

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

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