New redirect strategy

I change the way the redirect strategy works.
The redirects from authenticate/logout actions are now callbacks.
This way the user can overwrite the default callback and decide **exactly** what to should happen.

ping @Ocramius

closes #479
closes #476
closes #473
closes #469
If you make this thing a controller plugin (which I would advice), you can also reuse the url and/or redirect controller plugins. This just duplicates logic of assembling and returning responses