Applied in changeset tigase-pubsub|commit:2466c51a130a3530bec36ed1690ef084c2cb8258.

I modified adhoc command scripts and REST scripts to return errors also in format described in XMPP specification. Only difference in adhoc scripts errors is that they return stanza with type result but with error element added to return stanza. This error element contains error description. REST scripts processing this result will return only error element in case of error in following format:

<error type="cancel">
    <item-not-found xmlns="urn:ietf:params:xml:ns:xmpp-stanzas">Node test-123 needs to be created before an item can be published.</item-not-found>
</error>