Changes the courses page to include additional functionality

closes CNVS-14683, CNVS-14684, CNVS-14685

test plan:
   - Go to the courses page (/courses)
   - Make sure you have enrollments in various courses in various
     states (e.g., unpublished/published, past/future/current)
   - Each section (My Courses, etc.) should have a table within
   - My Courses should have stars in the first column
   - Clicking on a star should toggle the color of the star
     if the course is favoritable, e.g. students can favorite
     courses that are unpublished, while teachers can.
   - Stars that are colored yellow, should appear in the courses
     dropdown on the main navigation after a refresh.
   - The type of enrollment should be indicated on the far right.
   - Unpublished courses should have an indicator to the left
     of the enrollment type.
   - Hovering over the unpublished courses should have a
     tooltip saying:
     "This course has not been published. Students should contact
      the course instructor for access."
   - Screenreaders should also detect this information.

Change-Id: I660485b5143f877ef231b0edb52b2c82b8cdaab3
Reviewed-on: https://gerrit.instructure.com/39227
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>
Product-Review: Hilary Scharton <hilary@instructure.com>