Allow static media bundles to apply to certain URLs.
We previously only had one special type of static media bundle: "default".

This would appear on all pages. Extensions wanting finer page control

would have to use a TemplateHook with a set of URL names and a template

for loading the bundles, which was annoying and inefficient.
Now, static bundles can have an "apply_to" field containing a list of

URL names. When rendering default static bundles for a page, all bundles

matching that page's URL name will be included.

Tested with a custom bundle in an extension. Limited it to the review request

page and the diff viewer, and saw that it only loaded on those pages.