Issue #2089627 by tim.plunkett: Move \Drupal\system\SystemConfigFormBase to \Drupal\Core\Form\ConfigFormBase.
Issue #1945390 by Alan Evans, disasm, tim.plunkett, dawehner: Convert book_admin_edit() to a new-style FormInterface implementation.
Issue #1938316 by disasm, jaskho, stella, scor, tim.plunkett, jibran | Crell: Convert book_outline() to a new-style Controller.
