This change completes much of the re-styling and re-implementation of

the administration UI's Change Form pages. It adds specialized styling

for some Django admin form widgets to help them better fit into our

pages and updates existing styles to fix up some small layout issues.
It also updates the main change form template to remove legacy cruft and

to take advantage of our modern CSS components. As part of this template

rewrite, we no longer pull in the Django admin UI form CSS. An upcoming

change will scrap the remainder of the Django styles and overrides,

paving the way for Django 1.11.

Tested every change form for every model in desktop and mobile modes,

making sure everything rendered as expected.