Filter Errors on Change subject listener.
A unauthorized user sents a update room subject message which is
rejected by the server. It responds with an error message which
is not picked up by the ChangeSubjectListener.
Handle success SASL messages containing equals sign
More strict conformance to RFC 6120 § 6.4.6, correctly handle
success SASL message which consists of a single equals sign.
Fixes SMACK-737.
Rework blocking command code.
Mostly remove the helper utils. The server is required to present the
client with a consisent state of the block list and corresponding
modifications, so we should not end up with duplicate entires if we
don't check for them.
