When a whatsapp buddy sends an image, video or sound to the spectrum
user, the spectrum user will receive a URL that links to the media.
FileTranfer in spectrum is not working, apparently. Thus media cannot be
sent yet.
For some reason spectrum occasionally sends to identical messages to
a buddy, one to the bare jid and one to /bot. This causes duplicate
messages. Since it is unlikely a user wants to send the same message
twice, we should just ignore the second message.
This is only a work around, a proper fix should be implemented.
