DeadLetterQueue support not available when creating a queue

[rstradling]

On start-up we have a need for

  TestQueue {
    defaultVisibilityTimeout = 10 seconds
    deadLettersQueue {
      name = "TestDLQ"
      maxReceiveCount = 1
    }
  }

the deadLettersQueue part to be available to be set in the QueuesConf setting.

We have code that fails the tests because it is expecting the unacked message to show up in the DLQ and does not. We also need this change to be against 0.4.2 line of code for us.