Add FOSUserBundle events in ConnectController

I think it's a shame that not even a single event is dispatched on classic operations in this bundle. For instance, it would be very useful to have an event on registration.

As you seem to try to integrate the bundle into FOSUserBundle as much as possible, this PR links FOSUserBundle events in HWIOAuthBundle controllers. The connection action does not need an event as Symfony dispatch its internal one, but the registration may have one : in this PR, I use the FOSUserBundle one.

More globally, I would think of two possibles axes of development for this bundle : a better customization interface (events, external providers tagged in the DIC, ...) and above all a better an more complete documentation. It's really hard to set up this bundle and it could be dramatically improved.