Consistently highlight moderator/admin UI

[pushcx]

All mod UI needs to have some kind of unambiguously distinct and consistent visual styling. Maybe a 45 degree red/white striped background or underline? It’d be good to have a second, similar style for admin-only actions.

The moderator/admin UI is all inline to the Lobsters app, see the many .is_moderator? and .is_admin? calls in app/views and note that many call model methods that also use those methods. There’s some ambiguous UI like the edit link in stories/_listdetail.html.erb or flag summaries that can be present because the mod submitted the story or because they are a mod.