Qualtrics Survey Xblock

  Author fields in Studio:
   - Display Name
   - Survey ID
   - Your University
   - Link Text
   - Parameter Name for UserID

  If Parameter Name is left blank, the anonymous student id is
  omitted from the url.

  Links to an already existing Qualtrics survey.
I don't care for the name of this variable (particularly "your"). Also,
the value isn't simply "the name of your university". Given that it
appears in the URL, it's going to have limitations (no spaces, character
limitations). It could also be run on other instances which aren't
universities. Maybe something like:

```python
qualtrics_account_id = String(
    default="stanford",
    scope=Scope.settings,
    help="This is your Qualtrics account ID; https://QUALTRICS_ACCOUNT_ID.qualtrics.com/..."
)
```

We probably want to sanitize this input to escape any HTML too.