Better nginx config

Update the documentation to improve the sample nginx config chunks : 

 * Tweaks the headers to allow Bottle to properly set the host and scheme for the socket.io WebSocket server. This allows to use SSL (HTTPS+WSS) by simply proxying the web console through a HTTPS connection. The previous config still used plain WebSocket (``ws://*`` and ``http://*``) when the rest of the console used SSL (``https://*``)

 * Add a workaround to allow WebSockets to work when the console is protected by HTTP authentication. socket.io doesn't support WebSockets when the ressource is protected by HTTP auth (at least not natively). The server throws HTTP 401 error codes, breaking the live stat functionnality. A workaround is to disable HTTP auth for WebSockets.