Login via OpenID

Now this allow user to login via multiple OpenID accounts, I'll implement the web part after this and see if it will confuse the Interface part or I can fix it later if I find using just one account is more suitable. Any idea ? :)
I'm pretty sure that `->signed_fields` isn't what you want to pass to update_user.  Those are the internal fields of the OpenID response.

You'll also wnat to use `$vident->url` instead of `$vident->{identity}`.  Methods are better than looking at the internal object data.