Issue #2873696 by nvexler, wengerk, gido, Jo Fitzgerald, xjm: Add @internal to core classes, methods, properties to Form Classes

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 #2731861 by maxocub, felribeiro, aneek, alauzon, rajeshwari10, malavya, Sagar Ramgade, visabhishek, pashupathi nath gajawada, starshaped, quietone: Maintenance mode description shows wrong permission name

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

Issue #2570355 by Sutharsan, stefan.r, kgoel, josephdpurcell, joelpittet, justAChris, dawehner, pfrenssen, pwolanin, David_Rothstein, catch: Replace remaining !placeholder and @placeholder with :placeholder for URLs

Issue #2392319 by alexpott, effulgentsia: Config objects (but not config entities) should by default be immutable

Issue #2340251 by iMiksu, alexpott, tim.plunkett, dawehner, Wim Leers: Remove most remaining url() calls.

Issue #2239065 by tim.plunkett | webchick: Overridden config bleeding through to configuration forms.

Issue #2098119 by beejeebus, alexpott, chx: Replace config context system with baked-in locale support and single-event based overrides.

Issue #1786490 by Berdir, amateescu, damiankloip, Wim Leers, dawehner: Add caching to the state system.

Revert "Issue #1786490 by Berdir, amateescu, damiankloip, dawehner: Add caching to the state system."

This reverts commit 8ec847cc.

Issue #2089627 by tim.plunkett: Move \Drupal\system\SystemConfigFormBase to \Drupal\Core\Form\ConfigFormBase.

Issue #1981368 by tim.plunkett, Crell, webchick: Convert all routes to 'module_name().foo_bar()' naming convention.

Issue #2084339 by alexpott: Fixed The configuration value system.maintenance.enabled should be moved to the state system.

Issue #1925660 by ACF, tim.plunkett, mtift, heddn, Cottser: Convert system's system_config_form() to SystemConfigFormBase.