Prevent JavaScript errors on the Manual Updates pages.

The Manual Updates page tried to load the JS catalog, needed in order to
expose gettext() for the other scripts being loaded. That path wasn't
explicitly allowed, resulting in HTML being sent back as the script
contents, causing the browser to show some errors.

We may want to consider just blocking off all script loading. That will
require blocking extensions as well, though, and possibly daeling with
other corner cases. In the meantime, allow the JS catalog to be loaded.

Reviewed at https://reviews.reviewboard.org/r/5800/
Fix the styling of titles in the admin UI.

Titles in the admin UI were previously styled by the 'h1.title' rule,
which we replaced with '.box-title'. However, the admin UI doesn't use
boxes in the same sense as the rest of the UI, due to Django's built-in
styling.

This adds an explicit rule for titles in the admin UI, allowing them
once again to use the same styles as our other boxes.

Reviewed at https://reviews.reviewboard.org/r/5801/
Fix fetching original and patched files through the web API.

The handlers for getting original/patched files in the API were
expecting a URL parameter that doesn't exist. It would always attempt to
fetch using the draft filediff resource, instead of intelligently
choosing between that and the published filediff resource.

By using the correct URL parameter name, and using that parameter
correctly, we can fetch the original/patched files correctly.

Reviewed at https://reviews.reviewboard.org/r/5804/
Merge branch 'release-2.0.x'