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)

I think there's a better way to do this.

From the wiki [0]:
```python
course_key = SlashSeparatedCourseKey('org', 'course', 'run')  # Old-style identifiers
```

Which would give us:
```python
org = request.POST.get('org')
num = org = request.POST.get('number')
run = request.POST.get('run')
course_key = SlashSeparatedCourseKey(org, num, run)
```

Except in special cases, we want to avoid using `*_deprecated_*` methods.

[0] https://github.com/edx/edx-platform/wiki/Locators%3A-Developer-Notes#constructing-opaque-keys-by-hand