Backbone version of the course outline page

STUD-1726

Converted the course outline page to Backbone so as to support dynamic client-side updating.
Instead of calling compute_publish_state, @nasthagiri would like us to call has_item on the modulestore with the published_only enum flag (revision=ModuleStoreEnum.RevisionOption.published_only). We are working to get rid of compute_publish_state. Do you mind making that change?