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 #2309737 by rpayanm, hussainweb, max-kuzomko, herom, millerbennett, ianthomas_uk, quietone, Sutharsan, sumitmadan, toddmbloom: Remove deprecated format_plural usage

Issue #2340667 by YesCT, Pedro Lozano, alexpott, martin107: Protect Drupal\Core\Language\Language::id, and use getId().

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

Issue #2149197 by penyaskito, mikey_p, vijaycs85, herom: Replace format_interval with \Drupal::service('date')->formatInterval().

Issue #1957312 by ParisLiakos, peximo, Désiré: Use the entity storage controller in aggregator module.

Issue #1878302 by martin107, InternetDevels, nick_daffodil, chrisroane: Use 'delete' over 'remove' in the aggregator module.

Issue #2028039 by ParisLiakos, jsbalsera, undertext, mcrittenden, xeniak, amateescu: Expand ItemInterface (aggregator.module) with methods.

Issue #1957330 by ParisLiakos, twistor: Make possible for parsers and fetchers to expose configuration through plugins.

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

Issue #1754246 by webflo, swentel, penyaskito, andypost, alexpott, YesCT, dagmar: Languages should be configuration entities.

Issue #1986802 by yched: Rename PluginInspectionInterface::getDefinition() to getPluginDefinition().

This reverts commit c4e52bb6.