Implement JMS 2.0 shared subscriptions

JMS 2.0 has the feature of 'shared topic subscriptions', meaning two subscribers share a subscription and only one of them processes the messages. This is useful for situations where you need a pub-sub mechanism yet you want to have multiple instances of a single listener for failover/load balancing purposes, without having to filter out "duplicates" yourself in application code.

More info on shared topic subscriptions: http://www.oracle.com/technetwork/articles/java/jms2messaging-1954190.html

This is already implemented in Spring JMS:
http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/jms/listener/AbstractMessageListenerContainer.html#setSubscriptionShared-boolean-

It would be useful to have this property exposed on the publish-subcribe-channel as well.