Consider better organization for assignments

[braughtg]

• Need to revise many of the open responses as autogradable exercises.
  • Consider removing some questions as well.
• Assignments could:
  • be broken up by section to reduce the amount of stuff on the Runestone grading page.
  • identify key questions that instructors should check.
• Is there an additional tag for question title?
  • questions in Runestone grading page use the pretext id which is cryptic.