Allow users to view individual items when the full changeset view is too big (BB-2941)

When a changeset is too large to all be displayed on the page, you get this message:

//This changeset can not be displayed, as it is too large (cutoff was at 147.4 KB).//

In the list of changed files, each file is still linked to an anchor tag on the page that doesn't exist (because it was too large to display). So then the only way to see the diff is to manually browse to that file and select the diff to view.

Instead, the link should take you to the source view for that file, showing the diff of that changeset vs. its parent.

If a changeset is too large to show it all on the one page, make those links useful and take you directly to the diff for that file. If it isn't too big, have the links function as before, linking to anchors.