Issue #1712250 by alexpott, n3or, cam8001, vijaycs85, Albert Volkman, jibran, heyrocker, chx: Convert theme settings to configuration system.
Follow-up to #1712250: fix system_update numbering.
Issue #1292284 by ParisLiakos, RobLoach, karschsp: Require 'type' key in .info.yml files.
Issue #1987344 by tim.plunkett: NotFoundHttpException thrown in ParamConverterManager results in a WSOD.
Issue #1983844 by tim.plunkett, dawehner: Add EntityListController and convert picture.module callbacks to routes/controllers to provide a use-case.
Issue #1987298 by tim.plunkett, quicksketch: Shorten directory structure and PSR-0 namespacing for plugins.
Issue #1986888 by tim.plunkett, agentrickard: Fixed Field UI integration for entity types is brittle.
Issue #1988708 by andypost: Drop unused _taxonomy_get_tid_from_term()
Issue #1982020 by Fabianx, Cottser: Add static caching to drupal_html_class().
Issue #1549506 by swentel, pcambra, lbainbridge, muriqui: Fixed Edit and delete links should be hidden for locked fields.
Issue #1987604 by Wim Leers: Contextual's use of Drupal.formatPlural() doesn't allow strings to be detected, and minor cleanup.
Issue #1985386 by yched, Gábor Hojtsy: Crufty 'allowed_values_function_display()' ends up in list field stored config.
Issue #1938670 by ParisLiakos, Xano, RobLoach, pp, alexpott: Convert unicode.inc to \Drupal\Component\Utility\Unicode.
Issue #1696224 by aroq: Remove system_settings_form().
Issue #1984648 by tim.plunkett: Add AlterDecorator to TipPluginManager.