1.7.13 http listeners

[oliverhausler]

Added HttpListener

• With this change, netty-socket-io can be used for regular http requests on the same port, based on the path and without affecting socket.io.

I removed config.setAllowCustomRequests() as we can derive that setting from the number of HttpListeners being set (no listeners -> no custom requests).

Http requests are currently not wired through the AuthorizationListener, only socket.io requests. We may need to manage this or add a second AuthorizationListener. Not sure.

Code also needs to be documented, but I would want to get a first feedback, and if you want to merge this at all.

Improved AuthorizationListener

• In case of a redirect or error, the AuthorizationListener can now respond with a complete response, which gives control over response status, body and headers. A socket.io request can be terminated early or redirected, or a specific error status can be returned to the caller, without establishing the socket.io socket at all (which would be quite expensive).
• The AuthorizationListener can seed the client store. Instead creating an empty store after authorization, setClientData() will put data into the client store, which can later be retrieved as client.get().

PR is based on 1.7.13 (last stable version).