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.
Aliasing `QualtricsSurvey` to `cls` is confusing. Can we keep this named `QualtricsSurvey`?