A number of important accessibility changes

Reviewed by @brianhw https://rbcommons.com/s/edx/r/17/

lms - adds back in missing/previously added .sr screen reader-focused styling and references in place of the .visuallyhidden application

adds in status for overall problem status indicator and replicates needed correctness django logic to show individual choice status

courseware active location, suppress browser form validation, and progress graph accessibilit changes

Will/jenkins diff cover

Have the draft module store actively prevent non-leaf nodes from being

Fix encoding errors when hashing XML

In these tests, 'rendered_html' is neither rendered, nor HTML.  Name it context_repr, since that's what it is.

Feature user-management autoenroll

Use repr instead of str for getting context data via the system render function, so it works better for non-ASCII data.