19673 - remove topicprefix, queueprefix, and topicsep

The old stomp connector tried to be configurable by letting you
pick how a target like /topic/foo.bar would look using the topicprefix
and topicsep options.  Ditto for queues using queueprefix.

We've come to the conclusion that a generic stomp connector will just
never work well and removed that connector.  This commit removes these
unused settings too