Have a callback function like analyticsMore for all service

[maximehuran]

I think the idea of a callback is nice and it could be extended to all services.
We could have a callback and foreach service we will have something like this :

            if (typeof tarteaucitron.user.callback === 'function') {
                tarteaucitron.user.callback();
            }

It can be an alternative to tarteaucitron.launch["myservice"]