Issue #3275585 by dspachos, apaderno, joachim: Implementations of getInstance() return the wrong type

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 #2665992 by alexpott, klausi, heykarthikwithu, xjm, tstoeckler: @file is not required for classes, interfaces and traits

(cherry picked from commit 5da78abd)

Issue #2368349 by Gábor Hojtsy, alexpott: Entity view and form display configuration schemas are too verbose / key ones missing

Issue #2318281 by tim.plunkett, dawehner | kim.pepper: Provide a standard way to check a plugin is an instance of the required interface.

Issue #2204325 followup by Arla: Fixed The "rendered entity" formatter breaks for entity types with out a ViewBuilder.

Issue #2005434 by alexpott, heddn, andrewmacpherson, swentel: Let 3rd party modules store extra configuration in EntityDisplay.

Issue #2178795 by tim.plunkett, jlbellido, YesCT, Berdir, Xano: Allow DiscoveryInterface::getDefinition() to throw an exception for an invalid plugin.

Issue #2136197 by andypost, jessebeach, swentel, longwave, Berdir: Move field/instance/widget/formatter settings out of annotation / plugin definition.

Issue #2053153 by tim.plunkett, dawehner, damiankloip, aspilicious: Allow contrib modules to provide plugins on behalf of optional modules.

Issue #2050835 by Berdir | yched: Move Widget, Formatter, and FieldType plugin types to the Core\Field system.

Issue #1847002 by tim.plunkett, effulgentsia, msonnabaum: Move entity type classes from Drupal$provider\Plugin\Core\Entity to Drupal$provider\Entity.

Issue #2051847 by dawehner: Fixed AnnotatedClassDiscovery::getDefinitions is critically slow when viewing nodes with comments.

Issue #1969728 by yched, effulgentsia, swentel, fago, plach: Implement Field API 'field types' as TypedData Plugins.

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 #1851706 by yched, effulgentsia, tim.plunkett: Fixed Make all core plugin managers be consistent as to whether  or ->discovery is passed to the factory.