Support for websocket

Created by: stephanemagnenat

In the current design, the new switch aims at supporting bare Aseba TCP connections for Aseba messages, as well as a full-featured, "high level", HTTP interface.

It would be helpful to add websocket support for Aseba message communication. That way, a stripped-down version of the switch, providing TCP and websocket, but not HTTP, could be quickly implemented in an embedded target such as the Thymio, while still allowing web applications to communicate with the robot, providing they properly implement the Aseba message protocol in Javascript.

Websocket payload messages can then be bare Aseba messages, with the source and the type but without the length, as it is part of the message websocket header.