Issue #1954892 by dawehner, tim.plunkett, David_Rothstein, effulgentsia: Replace 'theme callback' and hook_custom_theme() with a clean theme negotiation system.

Issue #2063401 by dawehner, damiankloip, tim.plunkett: Replace the default _access_checks()(access mode) with ALL instead of ANY.

Issue #2051097 by dawehner, Manuel Garcia, tlattimore, neclimdul: Change 'pattern' to 'path' in *.routing.yml files.

Issue #1981368 by tim.plunkett, Crell, webchick: Convert all routes to 'module_name().foo_bar()' naming convention.

Issue #2031385 by Wim Leers, Thomas Brekelmans: Fixed Editor's in-place editing AJAX endpoint broken because of #1043198 and routing system bug.

Issue #1879120 by quicksketch, Wim Leers, larowlan, frega: Use Drupal-specific image and link plugins — use core dialogs rather than CKEditor dialogs, containing alterable Drupal forms.

Issue #1886566 by Wim Leers, sun, effulgentsia, quicksketch: Make WYSIWYG editors available for in-place editing.