Feature: add callbacks for 'open/connect', 'close', 'error', 'message' socket events

[nstylo]

It would be nice to be able to hook into socket events, i.e. 'open', 'close', 'message', 'error' for websockets and 'connect', 'close', 'data', 'error' for ipc. For instance one might want to include logging on this lower level. I tried doing this by getting the SocketRpcClient and then accessing the socket field. But on close as well as on error a new socket is created and thus eventHandlers are cleared.