Websocket API: Map responses to requests

[fabiocaruso]

Currently, it seems that there is no way for the client side to determine to which request a response belongs. If the client sends two consecutive requests of the same type and the second request is processed faster than the first, the response of the second request is sent first, and the client needs to assume it's the result of the first request even though it's the result of the second. It would be great if there is some sort of id field, that uniquely identify a requests/responses. This can be done using JSON RPC like described here.