Auto adds user to user table if user registration enabled with ldap auth...

First pass at registration, etc for ldap. Right now uses the new field AUTH_USER_REGISTRATION to determine whether to auto-add new users that authenticate correctly via ldap. Missing documentation on new fields AUTH_LDAP_FIRSTNAME_FIELD and the like. Also missing is ability to pop user to registration page either via setting or if some settings fail in ldap (like say, can't get email address). 

Thoughts?