When the config forms stylesheet was moved into Djblets, some styles

specific to Review Board remained. As part of a major revamp of the

stylesheets, some of these styles are scheduled to be removed. This

change prepares for that by moving those styles back into Review Board,

and makes use of the config forms support throughout the Django admin

UI.

Tested that the My Account page looked as it did before after the

removal of these styles in Djblets, and that pages in the Admin UI

using the new config forms styles looked right.