Add review request details to the top of the diff viewer

Review Request #17 — Created May 20, 2007 and submitted — Latest diff uploaded

Review Board SVN (deprecated)
It's been requested that we display the change description at the top of the diff viewer. I'd agree, as this is pretty useful information. We now display a non-modifiable version of the review request box at the top of the diff viewer, containing the file index. Also added a link to the top-right of the box for quickly getting back to the review request page.
Made sure the details all showed up correctly and navigation between the two pages continues to work as expected.