Issue #1950632 by effulgentsia, Wim Leers, amateescu, yched: Create a FieldDefinitionInterface, decoupled from  and  config entities, and use it for formatters and widgets.

Issue #1987298 by tim.plunkett, quicksketch: Shorten directory structure and PSR-0 namespacing for plugins.

Issue #1930020 by dawehner, Berdir, olli: Inject a class into the Core annotated discovery implementation so that namespaces can be updated.

Issue #1836008 by dawehner, Berdir, alexpott, katbailey, effulgentsia, EclipseGc: Fixed Remove drupal_classloader() use in Drupal\Core\AnnotatedClassDiscovery.

Issue #1801304 by Amitaibu, amateescu, effulgentsia, tim.plunkett, EclipseGc, Fabianx, Cottser: Added Entity reference field.