Issue #1986802 by yched: Rename PluginInspectionInterface::getDefinition() to getPluginDefinition().

Issue #1998140 by dawehner, ParisLiakos, tim.plunkett: Remove backward compatible ControllerInterface.

Issue #1987066 by Kevin Morse, JohnAlbin, rteijeiro, echoz, ry5n: Rename files to match CSS file naming convention.

Issue #1957154 by joates, ayelet_Cr, xjm | Berdir: Replace calls to drupal_container()->get('module_handler()') service with Drupal::moduleHandler().

Issue #1898424 by joelpittet, duellj, Cottser, mr.baileys: layout.module - Convert PHPTemplate templates to Twig.

Issue #1938430 by shanethehat, steveoliver, Fabianx: Don't add a default theme hook class in template_preprocess().

Issue #1987298 by tim.plunkett, quicksketch: Shorten directory structure and PSR-0 namespacing for plugins.

Issue #1391694 by tim.plunkett, aspilicious, fago, pounard, plach, Crell, msonnabaum, tstoeckler: Use type-hinting for entity-parameters.

Issue #1930020 by dawehner, Berdir, olli: Inject a class into the Core annotated discovery implementation so that namespaces can be updated.

Issue #1807042 by tim.plunkett, effulgentsia: Rename entity storage/list/form/render controllers to handlers, part 1: organize existing annotation keys.

Issue #1849752 by effulgentsia, Berdir, jibran, neclimdul: Abstract non-Drupal-specific parts of AnnotatedClassDiscovery into a Drupal\Component base class.

Issue #1836008 by dawehner, Berdir, alexpott, katbailey, effulgentsia, EclipseGc: Fixed Remove drupal_classloader() use in Drupal\Core\AnnotatedClassDiscovery.

Issue #1851706 by yched, effulgentsia, tim.plunkett: Fixed Make all core plugin managers be consistent as to whether  or ->discovery is passed to the factory.

Issue #1331486 by katbailey, chx, sun, beejeebus, amateescu: Move module_invoke_*() and friends to an Extensions class.

Revert "Issue #1331486 by katbailey, chx, sun, beejeebus, amateescu: Move module_invoke_*() and friends to an Extensions class. Broke core tests after commit."

This reverts commit c80c3e18.

Issue #1331486 by katbailey, chx, sun, beejeebus, amateescu: Move module_invoke_*() and friends to an Extensions class.

Issue #1764278 by tstoeckler, tim.plunkett, yched: Fixed Run PluginManagerBase::processDefinition() in a ProcessDecorator.

Issue #1817044 by sdboyer, effulgentsia, tim.plunkett, Gábor Hojtsy, yched: Implement Display, a type of config for use by layouts, et. all.

Issue #1814520 by seutje, DesignDolphin, Stalski, JohnAlbin, jenlampton, swentel: Create 2 basic sample layouts: 1-col and 2-col.

Issue #1787846 by Gábor Hojtsy, EclipseGc, effulgentsia, fubhy: Added Themes should declare their layouts.