UP-4046 Support RENDER_HEADERS, Dynamic Skin to use it
UP-4046 Support RENDER_HEADERS - incorporated pull request feedback

Also
- removed references to show sticky header in detached mode (detached has only one view now)
- removed obsolete references to header and footer portlets in fragment-layout files
Merge pull request #302 from jameswennmacher/UP-4046RenderHeaders

UP-4046 Support RENDER_HEADERS, Dynamic Skin to use it