Initial draft with UI changes

@gwprice and @mhoeber , this still needs changes to policy key settings/new images for the Studio changes that will be in tomorrow's release. Also, most of the paragraphs are not wrapped onto new lines, but I didn't want to distract from where I actually made changes. I'll do that later.
I think this is the only mention of cohorts we currently use in the docs. Maybe better to omit the mention here, and include the ability if we fully write up/release cohorts? Otherwise it's just an intriguing tease!