Authentication Backends

[psychcf]

We should implement authentication backends. This would allow the system to authenticate via LDAP, a CMS usertable, etc. If no authentication backend is provided, it will use our own internal user authentication system.

[psychcf]

This can be easily done by checking the designated backend during $User->authenticate(). We will still use our own tables to store userdata, but passwords will be checked through authentication backends. We do need to set it up so multiple password encryption methods (or none at all) can be used during authentication, depending on the authentication backend.

Now, as for openID, I'm not sure how to implement that since it uses a remote site to authenticate (we cannot directly look up a user's password).