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.
Thinking about this a bit more, I don't think that being designated a discussion administrator is sufficient to actually be able to manage forum roles. The reason for this is that the only UI we currently expose for managing roles is the Instructor Dashboard, which is only available to instructors and allows any instructor to modify all forum roles.