This fixes a bug where feedback email message is sent with multiple reply-to
addresses when (1) sender email address was supplied via the feedback form and
(2) override_from is configured in config.ini > Mail.

- Loads the facet data on demand asynchronously, potentially improving performance.

This reverts commit 1070d1ab.

- Adding data-lightbox-image attribute.
- Checks data-lightbox-href/href/src for a URL that links to an image.
- Puts url in img tag.
- Wraps img with .lightbox-image div.