“Sensitive content” warning cover for content and context modules.

• when adding/editing an item add a “sensitive content” checkbox field. Visible to admins and moderators by default.
• when sensitive content item is opened show a full page popup that covers the content and shows warning: “This content may be inappropriate for some audiences. Would you like to view it anyway?” Yes and Cancel buttons. Yes closes popup and Cancel redirects to site homepage.
• Also make sure that it works correctly on browsing pages, timeline feeds, no autoplay in timeline for such content, etc....