The new WFD RTSP handling code

This PR contains multiple commits introducing wisywidi library which encapsulates WFD RTSP handling code (parser, state machine) and exports convenient interfaces to the client.
This would be added as a separate PR, after API changes in https://github.com/alexshalamov/wysiwidi-2/commit/ee39dab66068dda4fbe0014d99baca3ec299bc2d