DRY up route for identities
Add P3P encoded privacy policy

Fix for github issue number: #37.  The addition of a P3P privacy
file and the accompanying http header will force IE version 9 to accept
cookies when DocumentCloud is loaded into an IFrame.

Nginx will also need to have an add_header line added to it's
configuration.  I've made the change in the documentcloud.conf
template file; it will also have to be applied to existing servers.
Header name for P3P was incorrect.  This is tested working with IE 9.
Add explanation of what the policy indicators mean.

The HTML file is generated by the IBM P3P Policy Editor.  The editor is no longer hosted on IBM's website, but can be downloaded from: http://www.softpedia.com/dyn-postdownload.php?p=160916&t=4&i=1

You can load up the XML file from app/views/home/p3p.xml into the editor and change the preferences from there.
Login via an iframe

Supports logging in either using a documentcloud account or third party authentication services.

External users can login to documentcloud by placing an iframe by using the easyXDM javascript library with the provider iframe pointing to documentcloud.org/auth/iframe.