Allow handling of non-websocket HTTP calls.

[Danielku15]

It would be nice to have some sort of "Fallback-ProtocolProcessor" to handle any HTTP calls that might have come from the user. From what I could see is this would perfectly fit into the WebSocketProtocolProcessor chain. All WebSocket protocol processors will fail on a normal HTTP call. In this case the "Fallback-ProtocolProcessor" could kick-in and handle the normal HTTP call by loading and returning some data.

Our plan is to add a simple REST API in parallel to the WebSocket connection which allows us querying some status information of the server (e.g. connected clients, data throughput etc.).

Sadly the protocol-processor chain is set-up hidden in the WebSocketServer.Setup method. I cannot see an easy way of adding a custom ProtocolProcessor to this chain.