new assignment index for course homepage

fixes CNVS-10988

test plan:
  - as a teacher with draft state on
    - set the homepage to show assignments
      - the homepage should look like student view
      - it should look good
      - it should function normally
      - you should be able to change the homepage to another view
    - view it as a student
      - it should work normally
  - as a teacher with draft state off
    - the homepage should look like the old one
    - it should function as usual
    - you should be able to swith the homepage
  - the actual DS assignment index page should work normally
  - set multiple due dates for assignments
    - teacher should see multiple dates
    - students should see their date only
    - try to break this somehow
  - on the homepage
    - if you have it full screen, date available until should be there
    - if you shrink the screen to a size where there is overlap AND reload
      - date available until should go away so there is no overlap

  - make a several assignments with different grading types
    - teacher & student homepage grade column should look okay

Change-Id: I4ff101c05d18592a5c92dc2650eee406116ba4c5
Reviewed-on: https://gerrit.instructure.com/31522
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Hilary Scharton <hilary@instructure.com>
Reviewed-by: Liz Abinante <labinante@instructure.com>
QA-Review: Amber Taniuchi <amber@instructure.com>