Prep marketing iframe and relevant courseware view for email opt-in

Puts a checkbox in the iframe. The iframe uses an organization_full_name parameter sent by the courseware views and POSTs an email_opt_in parameter to the student views, preserving it on 403.

Adds tests, modifies view to receive organization full name from GET parameters
Thanks, however after thinking about it more the elements will need a wrapper for positioning. Could you please wrap it in a paragraph element with the class form field?
///
<p class="form-field">
    <input id="email-opt-in" type="checkbox" name="opt-in" class="email-opt-in" value="true" checked>
    <label for="email-opt-in">
</p>
///