Changeset 1001 for sites/trunk/wordpress.org/public_html/wp-content/themes/pub/wporg-themes/view-templates/theme-single.php

WP.org Themes: Bring theme installer goodies to the front-end.

This brings most of the Backbone and Themes API-based functionality
from the admin's theme install screen to the front-end.

There are of course still loads of things to do, but it works
decently enough to share it with the world and give an idea of where
this is headed.

See ​https://make.wordpress.org/meta/2014/11/20/theme-repository-theme/
See #745.