Enable use of Django admin widgets from extension configuration pages.
The Django admin forms have some very useful widgets that one may want

to pull in. However, it also needed some additional files imported and

variables declared first. It's now possible to use these widgets.
It also makes it possible to define a Media class in a form and include

that media in any siteconfig settings page. This is a standard form

feature we just weren't supporting.
This does require a 'scripts-post' block in a base template to use this

support.

Tested with a couple admin widgets on an extension configuration page.