CQS: accessible report generation

This patch makes the report-generation functionality more accessible to
screen-reader and keyboard users. It also uses qTip instead of the old
jQueryUI.tooltip library we're using in Canvas for reliable keyboard
support and repositioning.

I'll highlight changes in the test plan.

Closes CNVS-15110

TEST PLAN
---- ----

Prepare for tests:

  - create a quiz with any number of questions
  - go to statistics cqs

We want to see if we can generate the reports using only the keyboard,
and another time without looking at the screen at all.

> Drive 1: generating the report using only the keyboard

  - use TAB to reach the "Student Analysis" generation button
    + verify the tooltip automatically opens as soon as you focus the
      button
    + press ENTER/RETURN
      - verify the report generation begins
      - verify the tooltip adjusts its position as the content changes
      - when it's complete:
        + press ESCAPE to close the dialog
        + verify that the focus is still locked to the button (which is
          now really a link)
        + click ENTER/RETURN
          - verify you get the Save-As file prompt
          - tooltip should now read "Report has been generated." or
            similar

> Drive two: generating the report with eyes shut

  - Turn on NVDA, JAWS, or VoiceOver
  - don't look at the browser! only these instructions
  - hit TAB until you hear "Generate item analysis report, button"
  - press ENTER/RETURN
    + you should soon hear "Report is being generated"
    + if you're lucky[1], you will hear the following updates:
      - "Less than half way to go" (when it's 50-75%)
      - "Almost done" 75-99%
      - "Report has been generated." at 100% and just before the button
        gets converted into a link
    + when it's done, you *should* hear "Download item analysis report,
link"
    + you should be prompted to save the file as usual
    + now when you close the dialog, if you TAB once, you should hear:
      - "Report has been generated."
  - reload the page
  - TAB a bit until you get to any of the (already generated) reports:
    + you should hear the "download..." message
    + if you TAB again, you should also hear *when* it was generated,
      something like: "Generated: Sunday ..."

[1] Even for quizzes with 400+ submissions, the report on my machine
would be generated in less than a second so I could not reliably get the
progress update messages to read all the time so it wasn't really
useful. YMMV. If you try this many times though, you'll at least hear
enough variations. Presumably, on production things take longer and
this will be more useful.

Change-Id: Ie879c20f5621e22b1b506f14e40877cf55eafb86
Reviewed-on: https://gerrit.instructure.com/40685
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Trevor deHaan <tdehaan@instructure.com>
Reviewed-by: Derek DeVries <ddevries@instructure.com>
Product-Review: Ahmad Amireh <ahmad@instructure.com>