CQS - Expand/collapse question answers

Adds buttons to expand and collapse the question answer drilldown.

Closes CNVS-15054

TEST PLAN
---- ----

  - create a quiz with a bunch of MC/TF questions
  - take it
  - go to cqs page (/courses/:id/quizzes/:id/statistics_cqs)
  - under the Question Breakdown section:
    - verify each question box contains an "expand" button
    - click it
      + verify you see the answer drilldown below that matches the Ember
        one
      + click the button again (which should now show a Collapse icon)
        - verify the drilldown is now hidden
  - click the toggle button right next to the "Question Breakdown"
    heading
    + verify it expands/collapses all questions
      - play around by expanding/collapsing individual questions and
        then use the master one, it should always get them *all*
        expanded or *all* collapsed

Change-Id: Icf7fe571356c02c2d85b1dc2b6396c71f5281515
Reviewed-on: https://gerrit.instructure.com/39858
QA-Review: Trevor deHaan <tdehaan@instructure.com>
Reviewed-by: Derek DeVries <ddevries@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Ahmad Amireh <ahmad@instructure.com>