[SàT dev][en] Implementation XEP-0070

[Geoffrey]

> That looks great thanks ! I'll merge it in 0.7 quickly. Is there any test 
> website to try it ? Answer me in private if the website should not be public.
I don't know any website that using it for now. I will integrate it in
my home automation central.
But in order to test it, there are my server implementation at
http://auth.xmpp.kingpenguin.tk (source code at
https://git.kingpenguin.tk/chteufleur/HTTPAuthentificationOverXMPP to
see how to use it).

Geoffrey