Better feedback for filetransfer
When a stream negociation fails, for some reason, the xml stanza that is send back to the client may contains a error message ( example 8 from jep 0095 ):
\<iq type='error' to='sender@jabber.org/resource' id='offer1'>
\<error code='403' type='cancel>
\<forbidden xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
\<text xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'>Offer Declined\</text>
\</error>
\</iq>
gajim should show this error message, as it may provides information about the failure.