Issue #2776975 by joelpittet, dawehner, tim.plunkett, xjm, pfrenssen: March 3, 2017: Convert core to array syntax coding standards for Drupal 8.3.x RC phase

Issue #2820743 by damiankloip, dawehner: FieldNormalizers are very unforgiving, impossible to debug error response given

Issue #2827218 by tedbow, damiankloip, Wim Leers, Berdir, tstoeckler: Denormalization on field items is never called: add FieldNormalizer + FieldItemNormalizer with denormalize() methods