Initial commit for always cohort inline discussions plus spelling fix

I'd revise the passive voice in this paragraph:

This means that, when a student in a cohort creates a post on a content-specific topic, only members of that same cohort can read and respond to the post (or "This means that only members of the same cohort can read and respond to each others' posts on content-specific topics"). In contrast, any course-wide discussion topics that you set up for your course are unified by default. This means that every student can read and respond to all posts for course-wide discussion topics.