Switch to form based login and adjust session management

Because the session support of atmosphere seems to be conflicting with spring security, it is disabled now. As a consequence, native web sockets must be disabled, too. In some scenarios this will be no brainer because both long-polling and SSE supports directly session and have no problems when using load balancers in front of a cluster.
Merge branch 'spring-security-3.2' into clustering
Replacing atmosphere-redis adapter with a custom one

Because the atmosphere's redis adapter requires configuration in the web.xml, the replacement externalized the configuration into a property file. This makes the module atmosphere-redis adapter obsolet (no extensions possible).

Usage of `atmosphere.xml` is not possible because of the presence of `MeteorServlet`.