Issue #697760 by sun: Replace getInfo() in tests with native phpDoc + annotations (following PHPUnit).

Issue #2286403 by martin107: Inconsistent use of magic number when constants DIRECTION_LTR and DIRECTION_RTL already defined.

Issue #2246665 by jaredsmith, martin107, YesCT, filijonka, tstoeckler: Typehint with Drupal\Core\Language\LanguageInterface instead Drupal\Core\Language\Language.

Issue #1067408 by alexpott, Jalandhar, jessebeach, Désiré, neetu morwani, dawehner, sun: Themes do not have an installation status.

Issue #2208609 by sun, Jalandhar, damiankloip: Move Json utility class into Drupal\Component\Serialization.

Issue #2161591 by pwolanin, beejeebus, sun: Change default active config from file storage to DB storage.

Issue #2219499 by Berdir, alexpott, Gábor Hojtsy, vijaycs85, swentel: Generalize language config override responsibility.

Issue #2164367 by alexpott, tim.plunkett, dawehner: Rebuild router as few times as possible per request.

Issue #2098119 by beejeebus, alexpott, chx: Replace config context system with baked-in locale support and single-event based overrides.

Issue #2031175 by Sutharsan, penyaskito, vijaycs85, Berdir: Translation imports take a lot of time in tests even when not needed.

Issue #1952394 by vijaycs85, tstoeckler, webflo, Gábor Hojtsy, Schnitzel, falcon03, YesCT, kfritsche, Ryan Weal, dagmita, likin, toddtomlinson, nonsie, Kristen Pol, dawehner, tim.plunkett, penyaskito, EclipseGC, larowlan, robertdbailey, helenkim, David Hernández, EllaTheHarpy, lazysoundsystem, juanolalla, R.Hendel, Kartagis: Add configuration translation user interface module.