Add additional information regarding session states

Pulling in the session state requests from https://issues.jboss.org/browse/JBEAP-12656.

But I understand this issue as request getting into documentation that:

• we provide option org.wildfly.security.http.state-scopes
• example how can be this option configured
• what are valid values for this option?
  • CONNECTION,SESSION,NONE
• what is meaning of these options? What are pitfalls of this options?
  • CONNECTION - e.g. state is hold on TCP connection. There is problem with using with load balancer. *
  • SESSION - e.g state is hold on http session. *
  • NONE - e.g. state is hold on request. Unable to handle continuation required. *
• what is default value?
  • SESSION

"*" For proper wording consult with devs

Most of these things is covered in KB already. Just need to transform to documentation in bug-agnostic way.