basic gatling test
some changes to improve scalability

 * don't use managed executor service, too low defaults
 * use application managed JMS connection (jms-message-helper) also for sending, avoid issues with managed pool size
 * Remove some messages from the public UI to make the test more easier to implement (deterministic amount of messages from the server)
 * keep atmosphere (and vaadin) happy by closing web socket with a special XHR
work in progress
A version that uses infinispan listeners instead of JMS for eager updates