Assignment work in progress

Signed-off-by: reggiejr <reggiejr@umich.edu>
initial changes to challenges
initial changes
initial changes to challenges
initial changes
analytics a11y fixes
Initial accessibility changes to Assignments
Initial accessibility changes for Course
Added disambiguation to buttons in Grading Status
Added caption to table
add missing describedby
Changing %a to link_to with a block
Changing %a to link_to with a block
change scope from col to row
rename class for sr-only text
revert %a to link_to
AJ-2302 Sort display tiers by points on assignment page, ascending left to right.
AJ-2262 working on absolutely repositioning delete button
Accessibility changes to Course Index page
AJ-2262 Increase rubric padding to accommodate delete button