Make changes based on edX accessibility review

Add accessible percentage selected information to graphs options/legend.

Change headings to conform to edX standards.

Change contrast ratios (headings, progress bar, steps labels).

Fix some previously non-unique IDREFS.

Use edX "sr" class to make notion of progress accessible.

Make chevrons in progress bar children of list items, with aria-hidden
as false.

Add padding above QUESTION heading.

Make PI heading capitalized, with points weighting text on same line.

Fix aria-labelledby reference.

Make progress bar use an ordered list.

Add aria-hidden="true" to icons.

Clarify role of progress bar by adding <div role="group"
aria-label="Progress Indicator">.

Fix caps and accessibility for progress bar

Move spans within lis.

Tweak wording

Make graphs and progress bar accessible

Fix caps, ul, and role

Handle non-integer values for number of answers

Handle non-integer values in Studio for number of answers shown to
students.