module-filewrite: remove dead code
transport-xmpp: Remove outdated comment
transport-xmpp: s/jid/masterJid/
transport-xmpp: Avoid sending messages to excluded resources

If the excluded resource is the only online presence for a master JID,
the we should not send the message to this JID. This means that under
certain circumstances, such a master JID will not receive offline
messages, but users who configured excluded resources usually don't care
for offline messages anyways.

MAXS-10