UP-3501 Removed the new user link for CAS logins

UP-3501 Removed the new user link for CAS logins since you can't actually create an account. The link just took you to http://jasig.org/cas.

There is info on the front page of the portal about how to login and what accounts people can use, so they can still login.

This also resolves UP-3249 since the text no longer appears.

Screenshot of what it looks like afterwards: https://skitch.com/steveswinsburg/edwg8/uportal-welcome