Fix: force File page images to wrap
• Limit the width of file page images to available space. e.g.,
http://localhost:3000/wiki/File:Buffer_zone.jpg on smaller screens.
• Forbid surrounding content from appearing on the same line as File
page images. e.g., http://localhost:3000/wiki/File:Buffer_zone.jpg on a 1024px screen. Note: A "block" prop was added to Thumbnail to show it as a block in desktop widths. In the wiki page is the only place that Thumbnails should be presented this way. e.g., images should still float on the summary page on 1024px screens: http://localhost:3000/page/summary/Bill_%26_Ted's_Excellent_Adventure.