Various open ended accessibility fixes

...b/xmodule/xmodule/js/src/combinedopenended/display.coffee

...pen_ended_grading_classes/combined_open_ended_modulev1.py

...e/xmodule/open_ended_grading_classes/open_ended_module.py

...dule/open_ended_grading_classes/self_assessment_module.py

...mplates/combinedopenended/combined_open_ended_status.html

lms/templates/combinedopenended/openended/open_ended.html

...plates/combinedopenended/openended/open_ended_rubric.html

...binedopenended/selfassessment/self_assessment_prompt.html