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
Same as above. I understand the BC concerns, but this is really overkill. Maybe get rid of it later (2.x)?