Make section drag&drop in course main content area compatible/synchronize with course index

As a teacher
I want to be able to move a section using drag and drop and see the change applied in the course index
so I don't need to reload the page to confirm the changes were properly applied.

Acceptance criteria:

1. The order of the sections is synchronized between Course index and course main content area.
2. The order of the activities in each section is synchronized between Course index and course main content area.
3. When a section is dragged in course main content area and moved to another position in course main area content acceptance criteria 1) and 2) should be consistent.