Use native WebSocket client instead of socket.io client.

Make sure webSocketUrl is resolved to the correct relative path, with the right protocol and port, by renaming resolveRelativePath to webSocketUrl, which works as a self executing function, in order to avoid syntax clutter in the line below.
Message on raw web socket events are nested on data-attribute.
Extracted web socket error handler into it's own named function.
Don't include the socket.io client in the inspector front-end.