INT-1197: Add Support for WebSockets: Client Side

JIRA: https://jira.spring.io/browse/INT-1197

INT-1197: Add JavaDocs and some polishing

Further changes

* Upgrade to SF 4.1
* Rename `SubProtocolHandlerContainer` to the `SubProtocolHandlerRegistry`
* Add `MessageConverter` support to the adapters
* Add `ClientWebSocketContainer.openConnectionException` to be thrown on `getSession` request
* Add `ClientWebSocketContainer.connectionLatch` to wait the connection establishing on first request.
Since the WebSocket connection process is run in the separate Thread, we need to wait it from the first `message send` do not lose the message, if connection hasn't been established yet.

INT-1197: Add `PassThruSubProtocolHandler`

Add `StompIntegrationTests`

INT-1197: Polishing according PR comments

INT-1197: Use SockJs from tests

Fix other detected vulnerabilities

INT-1197: `@Gateway` with `@MessageMapping` test

INT-1197: PR comments

Skip non `SimpMessageType.MESSAGE` to send to the `outputChannel` from `WebSocketInboundChannelAdapter`

Polishing