Register oauth hooks for global events that can be used in Config::Events

[evansharp]

Many CI events are hookable in Config::Events. Shield builds on this native system to by adding hooks like register and login. I noticed that the Sheild register hook is not called when a user is registered via oauth.

Perhaps this and a few other hooks would be a good addition.

[evansharp]

When I realized how easy this would be, by just using the hooks Shield already exposes, I went ahead an added the one I wanted in PR #196