show auth user in form_data view

dependent on https://github.com/dimagi/commcare-hq/pull/1750

this makes it easy to tell whether a form was submitted with authentication
No auth:
![screen shot 2013-11-06 at 8 40 23 pm](https://f.cloud.github.com/assets/137212/1485299/f7b64c4e-4712-11e3-86be-74415e08091d.png)

Yes auth:
![screen shot 2013-11-06 at 5 42 57 pm](https://f.cloud.github.com/assets/137212/1483583/333523d0-46fa-11e3-8ec4-53dad2c98687.png)

**Tested** by going through a number of form submissions locally—auth/non-auth, mobile workers, web users, admin, demo_user—and making sure it looked right (and didn't 500!)