Add WebSocket support

Add WebSocket Support in TrafficServer.

websocket is enabled on a remap basis, you will setup a websocket mapping by specifying the ws:// or wss:// schemes, for example add the following to remap.config:

map ws://127.0.0.1:8080/foo ws://127.0.0.1:9090/

Next, the current number of websocket connections can be monitored via the stats variable proxy.process.http.websocket.current_active_client_connections

Community feedback would be appreciated.