Added revision id so that the file and rev is displayed at the top before the diffs. This is useful for _some_ SCMs that have integer per file version numbers. For some of the distributed SCM's this may not be so useful.

Raising review as a discussion point, see http://groups.google.com/group/reviewboard/browse_thread/thread/89a89ece9d5e1139

Tested with SVN and another SCM (that uses integers for rev id's) that is not officially supported by ReviewBoard