Application Shutdown Event

[ChrisLongo61]

I would be nice if angular had an application shutdown event.

[lgalfaso]

There is no real way to destroy an angular application, (well, at least until #8005 or any of the other PRs that aim at this lands), so I am not sure what this issue is aiming for. That said, whenever any of these lands, the way to detect this would be by just listening on '$destroy' event on $rootScope. I am closing this as making an angular app shutdown friendly is handled in other PRs and the event would be there once any of these lands