Support static media bundles in review UIs.
ReviewUI now has css_bundle_names and js_bundle_names variables, which

specify static media bundles that will be loaded in when displaying the

review UI. This makes it easier to write a Review UI without having to

use a custom template to include the required files.
Extensions can use Extension.get_bundle_id to pass in bundle IDs for a

review UI, but it must do it in the ReviewUI's __init__ function, or

patch the class in the Extension's __init__, as the extension IDs (and

therefore bundle IDs) are computed once an extension is enabled and

constructed, not when defining the classes.

Added some random bundles to ImageReviewUI, and saw them load in the source

correctly.