Dead letter queue names should respect routing key

[elboletaire]

With changes done in #29 now we have different queues for each operator. However, maybe we should use the same format and set the deadLetterRoutingKey instead.

If we have one queue for each exchange + routing key, we should do the same for dead letters. Right now a new dead-letter is being created for each operator, which works, but is really what we want.

Also, consider removing the routing keys from the queue names (although it may not be possible in some cases, so do it carefully).