Improve spring-session to show that session replication

[vchintal]

@slaskawi The spring-session module is excellent to show how HTTP sessions could be saved in Infinispan caches but we aren't actually showing the value by demo'ing the session replication if a new spring-boot instance comes up and we hit the same context path. We should be able to show that session replicated and the same session ID is displayed as was created in the first spring-boot container.

I have the code ready, let me know if a pull request can be sent. Thanks!

[slaskawi]

I think that's an awesome idea! Pull requests welcome!