Improve handling of failing exceptionHandler

[mbknor]

If the exceptionHandler is failing, we are not acking the message, nor waiting some time before retrying. This results in 100% CPU loop (re)processing the same message and failing every time.
Need to have special handling of this situation, and possibly add slowdown

[jhberges]

My 10 øre:
Configure redeliver policies (either through connection URL, or config object), then just throw an unchecked exception and let the broker (well, client libs) deal with it. :-)

• http://activemq.apache.org/redelivery-policy.html
• http://activemq.apache.org/connection-configuration-uri.html (nested options)