In order for the Egg Template Loader to load templates from extension eggs, we must add the extension app_name to the INSTALLED_APPS list.

In order for Review Board to take advantage of this, "django.template.loaders.eggs.load_template_source" must be added to the TEMPLATE_LOADERS in settings.py.  I've made that change here:  http://reviews.reviewboard.org/r/1625/

The parent for this patch is still under review here:  http://reviews.reviewboard.org/r/1618/

Tested manually, and I can now pull up templates stored in extension eggs.