Base implementation

I'm not telling you to not implement it: I'm telling you to not implement it NOW.

Login procedures with redirect URI need strict validation of the redirect URI to prevent session. Here's a nice one for you:

 1. `http://evil.com/` presents a page to the user, user clicks a link and lands on `http://roave-website.com/login?redirect=http://roave-website.com/donate?target-user=12345`
 2. user logs in and automatically donates to the `target-user`.

This is something very simple to exploit.

For reference, see ZF-Commons/ZfcUser#480