Issue #2502621 by Pravin Ajaaz, hussainweb, Peacog, jhodgdon, ivanjaros: Replace implement notes with inheritdoc tag

Issue #2164601 by yched, jibran, amateescu, pfrenssen: Stop auto-creating FieldItems on mere reading of $entity->field[N]

Issue #2340667 by YesCT, Pedro Lozano, alexpott, martin107: Protect Drupal\Core\Language\Language::id, and use getId().

Issue #2225333 by Boobaa: LogicException in Drupal\hal\Normalizer\FieldItemNormalizer does not exist.

Issue #2076445 by plach, andypost, yched, Gábor Hojtsy: Make sure language codes for original field values always match entity language regardless of field translatability.

Issue #2047229 by fago, smiletrl, Berdir, effulgentsia, amateescu: Make use of classes for entity field and data definitions.

Issue #2051923 by Berdir, dixon_, plach: Rename \Drupal\Core\Entity\Field\Field, related subclasses and interfaces to *FieldItemList.

Issue #2061331 by yched, plopesc: Added helper methods getEntity() in FieldInterface / FieldItemInterface.

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

Issue #1620010 by dawehner, ParisLiakos, plach, jibran: Move LANGUAGE constants to the Language class.