Issue #1886448 by dawehner, sun, Berdir, ParisLiakos: Rewrite the theme registry into a proper service.

Issue #2045931 by PerthSam152, LinL, adsw12, joelpittet: Replace all module_exists() deprecated function calls.

This reverts commit cc84f390 - bad
commit message.

Issue #2089351 by thedavidmeister, meba: Convert all calls to check_plain() in core to Drupal\Component\Utility\String::checkPlain() in core/includes.

Issue #2100329 by cosmicdreams: Use \Drupal instead of Drupal to make IDEs and static code analyse tools happy.

Issue #1969572 by neclimdul, larowlan, hussainweb, dawehner, damiankloip, ParisLiakos, pwieck, Berdir, socketwench: Make Uuid a service.

Issue #1199946 by alexpott, fubhy, bojanz, steinmb, chx, catch: Fixed Disabled modules are broken beyond repair so the 'disable' functionality needs to be removed.

Issue #2084339 by alexpott: Fixed The configuration value system.maintenance.enabled should be moved to the state system.

Issue #1827112 by alexpott, vijaycs85, dawehner, cspitzlay, cam8001: Convert 'install_profile()' variable to Settings.

This reverts commit 8ce27f22.

Issue #2045923 by drupalrv, tim.plunkett: Replace all module_invoke_all() deprecated function calls in procedural code.

Issue #1998204 by tim.plunkett: Fixed config_install_default_config() is not safe to use in hook_update_N().

Issue #1856976 by andypost, Soul88, ACF, aspilicious, vijaycs85, dawehner: Convert language_count() to the state system.

Issue #1833022 by e0ipso, plach, YesCT, kfritsche, penyaskito, vijaycs85, nod_, cam8001: Only display interface language detection options to customize more granularity.

Issue #1754246 by webflo, swentel, penyaskito, andypost, alexpott, YesCT, dagmar: Languages should be configuration entities.

Issue #1988508 by katbailey: Stop pretending we support Symfony bundles when we really just have service providers.

Issue #1872876 by chx, fubhy, dawehner, alexpott, tim.plunkett: Turn role permission assignments into configuration.

Issue #1668866 by ParisLiakos, aspilicious, tim.plunkett, pdrake, g.oechsler, dawehner, Berdir, corvus_ch, damiankloip, disasm, marcingy, neclimdul: Replace drupal_goto() with RedirectResponse.

Issue #1852454 by patrickd, xjm, YesCT, Berdir, amateescu, Pancho, djroshi, dealancer, Wim Leers, jessebeach: Restrict module and theme name lengths to 50 characters.

Issue #1813762 by ParisLiakos, Jose Reyero, YesCT, japicoder, attiks: Introduce unified interfaces, use dependency injection for interface translation.

Issue #1998576 by beejeebus, alexpott, swentel: Make the config import process use full config trees again.

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

Issue #2002732 by Froelund, diarmy, drupalmonkey: Improve code maintainability by removing unused local variables - core/includes/update.inc.

Issue #1827448 by RobLoach, sun, jbrown, tstoeckler: Use __DIR__ instead of DRUPAL_ROOT where possible/sensible.

Issue #1712250 by alexpott, n3or, cam8001, vijaycs85, Albert Volkman, jibran, heyrocker, chx: Convert theme settings to configuration system.

Issue #1937600 by Berdir, rootatwc | webchick: Determine what services to register in the new Drupal class.