Fix Enrollment Email UI/UX

@jrbl @caesar2164 

Fixed enrollment email UI in Studio. The list of changes is as follows:
    - Test Email functionality: can now send yourself a test email from studio
    - Set default template button: can now click a button to replace email
        with the default template
    - UI changes: html ordering and structuring
                  Got rid of enable_default_email button. Pushed this feature
                  to the default template button

Things to note:
    - default template is stanford-specific.
    - minor test changes (since enable_default_email field is gone now)

![screen shot 2014-07-30 at 12 48 48 pm](https://cloud.githubusercontent.com/assets/3598201/3755213/a65ef2ce-1822-11e4-9b63-d01e16be444f.png)
![screen shot 2014-07-30 at 12 49 07 pm](https://cloud.githubusercontent.com/assets/3598201/3755214/a65f7c30-1822-11e4-8c06-cfdc32c476af.png)
![screen shot 2014-07-30 at 12 48 28 pm](https://cloud.githubusercontent.com/assets/3598201/3755215/a66022e8-1822-11e4-8005-c7200f417886.png)

Is this the style for the urls used generally in javascript? 

I thought that there was some machinery for passing the URLs in a variable, so they could be auto seeded from reversing urls.py or something. If that machinery exists for this bit of javascript, it would be preferable to use it so you don't have to repeat yourself (and because URLs can migrate around sometimes.) But if it's not already there, don't build it; this is adequate.