plugin XEP-0277: removed cleanXHTML on output data: - while it is mandatory to clean input data, output data sent by frontends should and need to be clean - cleaning all output data means that we can't send be sure that all the XHTML we send is not modified - it's a waste of resources as cleaning today reparse the data with lxml - behaviour may change in the future (e.g. having an option to use cleaning on output data)