Initial connection of student module with cms.

* Enable account creation
* Some code cleanups
* Fix access to nonexistent fields in the account creation view
* Formatting fixes

cms/templates/activation_invalid.html

@@ -0,0 +1,16 @@
+<%inherit file="marketing.html" />
+
+<%block name="content">
+<section class="tos">
+<div>
+<h1>Activation Invalid</h1>
+
+<p>Something went wrong. Check to make sure the URL you went to was
+  correct -- e-mail programs will sometimes split it into two
+  lines. If you still have issues, e-mail us to let us know what happened
+  at <a href="mailto:bugs@mitx.mit.edu">bugs@mitx.mit.edu</a>.</p>
+
+  <p>Or you can go back to the <a href="/">home page</a>.</p>
+</div>
+</section>
+</%block>