AMQP: FBP discovery messages should be sent on fanout exchange about msgflo

[jonnor]

This is a breaking protocol change. So far, as far as we know, only the projects under the 'MsgFlo' github organization uses this.

[bergie]

If the discovery thing becomes and exchange, it might also make sense to send the "Hello World I'm Here" message periodically and not only at start-up. This way coordinator can catch participants even if they started before coordinator joined the game

[jonnor]

I also think that when we do this breaking change, we should rename this queue to something msgflo instead of fbp. Because what travels along are not FBP runtime protocol messages, but msgflo discovery messages. There are many concepts which are closely related or reused, so that a whole service of MsgFlo participant can be seen as one FBP runtime - but I think this distinction will help understand the differences.

[jonnor]

@bergie see #30 for periodic sending of discovery messages

[jonnor]

More important now that periodic sending is (starting to be) implemented, #30