Revert "Issue #2002162 by klausi, eugene.ilyin: Convert form validation of users to entity validation."

This reverts commit 5b41b6f8.

Issue #2057869 by dawehner, jibran: Provide an alias for 'plugin.manager.entity' called 'entity.manager'.

Issue #2057589 by smiletrl, tim.plunkett, alexpott, dawehner: Rename ControllerInterface to ContainerInjectionInterface.

Issue #1497374 by yched, chx, amateescu, plach, Damien Tournoud, fago, swentel: Switch from Field-based storage to Entity-based storage.

Issue #1974492 by larowlan, jibran, disasm, tim-e, mdrummond, robeano, nick_schuch, wamilton, effulgentsia, tim.plunkett: Convert taxonomy_overview_terms() to a Form Controller.

This reverts commit 135f4e6a.

Needs more discussion.

Issue #2061979 by rhm50, InternetDevels: Replace user_access() calls with ->hasPermission() in contextual module.

Issue #2071957 by Wim Leers: Fixed Cannot change existing images or links through Text Editor's image/link dialogs.

Issue #2044583 by jlindsey15, Gábor Hojtsy, Wim Leers, Berdir: Add EntityChangedInterface to allow entities with 'changed' field to be properly cached.

Issue #1946348 by splatio, jibran, kim.pepper, David Hernández, tim.plunkett | mtift: Convert all of confirm_form() in comment.admin.inc to the new form interface.

Issue #2062363 by sergeypavlenko: Remove calls to deprecated global  in core/modules/system/tests/modules/form_test()/form_test().module.

Issue #2062011 by InternetDevels, Albert Volkman: Replace user_access() calls with ->hasPermission() in path module.

Issue #2046097 by Berdir, Gábor Hojtsy: Fixed Very long URL (>255) leads to PDO exception when translation source locations are updated.

Issue #1126000 by yched, swentel, catch: Fixed Document that we don't support partial entity updates.

Issue #2018411 by ParisLiakos, tim.plunkett, msonnabaum: Figure out a nice DX when working with injected translation.

Issue #2047619 by dawehner, pwolanin, tstoeckler, thedavidmeister: Add a link generator service for route-based links.

Issue #1969916 by Tim Bozeman, Wim Leers, Cottser, nod_: Fixed Remove drupal_add_js()/css from seven.theme.

Issue #2062009 by InternetDevels: Replace user_access() calls with ->hasPermission() in overlay module.

Issue #2077003 by Wim Leers: Fixed tableselect.js uses Drupal object, but does not include it in its closure.

Issue #2062015 by InternetDevels, phiit: Replace user_access() calls with ->hasPermission() in picture module.

Issue #2062027 by InternetDevels: Replace user_access() calls with ->hasPermission() in taxonomy module.

Issue #2061985 by InternetDevels: Replace user_access() calls with ->hasPermission() in entity module.

Issue #2062033 by InternetDevels: Replace user_access() calls with ->hasPermission() in tracker module.

Issue #2061987 by InternetDevels: Replace user_access() calls with ->hasPermission() in field module.