C++ client library in progress in reSIProcate tree

[Daniel Pocock]

I started on an async C++ client library based on asio and websocketpp

It is here on a branch, along with a unit test to show how to use it:

https://github.com/resiprocate/resiprocate/tree/b-dpocock-recon-kurento/media/kurento

It is working for the essential steps in a SIP call

Here in Object.hxx you can see the API methods I've implemented, it
isn't hard to add more using cut-and-paste.

https://github.com/resiprocate/resiprocate/blob/b-dpocock-recon-kurento/media/kurento/Object.hxx