Revert "Issue #2711353 by rakesh.gectcr, Jo Fitzgerald, quietone, chx, Yogesh Pawar, Pavan B S, biguzis, phenaproxima, mikeryan, vasi, iMiksu, Berdir, dawehner, benjy: Migrate never unsets existing data for content entitites"

This reverts commit 3d524aaa.

Issue #2711353 by rakesh.gectcr, Jo Fitzgerald, quietone, chx, Yogesh Pawar, Pavan B S, biguzis, phenaproxima, mikeryan, vasi, iMiksu, Berdir, dawehner, benjy: Migrate never unsets existing data for content entitites

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 #2783715 by claudiu.cristea, chx, mikeryan, heddn, phenaproxima: Entity destination ID schema should match entity ID definition

Revert "Issue #2783715 by claudiu.cristea, chx, mikeryan, heddn, phenaproxima: Entity destination ID schema should match entity ID definition"

This reverts commit 3348de12.

Issue #2783715 by claudiu.cristea, chx, mikeryan, heddn, phenaproxima: Entity destination ID schema should match entity ID definition

Issue #2225775 by vasi, quietone, phenaproxima, chx, penyaskito, mikeryan, esclapes, vprocessor, steinmb, Gábor Hojtsy, Marc Angles, bwinett: Migrate Drupal 6 core node translation to Drupal 8

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

Issue #2676222 by alexpott, johnrosswvsu: Move MigrationInterface out of the migrate\Entity namspace now they are plugins

Issue #1919468 by alexpott, Berdir: EntityManager::getAllBundleInfo() adds default entity_type_id bundle for entity types with bundles

Issue #2603010 by neclimdul, webflo, mikeryan: EntityRevision destination can explode with missing nodes

Revert "Issue #2603010 by neclimdul, webflo, mikeryan: EntityRevision destination can explode with missing nodes"

Cross-commit with another patch that changed arguments.

This reverts commit 1f0466c4.

Issue #2603010 by neclimdul, webflo, mikeryan: EntityRevision destination can explode with missing nodes

Issue #2590993 by mikeryan, webflo, svendecabooter, dixon_, phenaproxima: Create stub entities with proper default values

Issue #2560637 by phenaproxima, benjy, quietone, mikeryan, chx, neclimdul: Improve handling of uid 1 during migration

Issue #1392754 by tss, justAChris, jhodgdon: Comply with new documentation standards for @file for namespaced class files

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

Issue #2213451 by andypost, bdone, benjy, penyaskito, chx, claudiu.cristea, damiankloip, gregboggs, InternetDevels, jessehs, jhedstrom, marvil07, mikeryan, pcambra, Xano, YesCT: Update Migrate API in core