Issue #1822048 by dawehner, tim.plunkett, damiankloip, EclipseGc, martin107, neclimdul: Introduce a generic fallback plugin mechanism.

Issue #2228745 by Wim Leers, sqndr, nod_, undertext: Fixed Color module doesn't look for CSS files declared in a library.

Issue #2325801 by jibran, larowlan: Abstract contact module mail delivery out of form into a service.

Issue #2142441 by Garrett Albright: Fixed [Followup needed] CSS aggregator prepends data: URLs with paths.

Issue #2318677 by bluegriff | emma.maria: Fixed Password field focus is interfering with the password indicator strength bar.

Issue #2337619 by alexpott: Fixed Drupal\views\Plugin\views\query\Sql::buildCondition is checking for a non existing class.

Issue #2332885 by cs_shadow, Berdir, fago: Rename AllowedValuesInterface to OptionsProviderInterface.

Issue #2312093 by alexpott, yched, andypost, swentel | xjm: Rename FieldInstanceConfig to FieldConfig.

Issue #2063303 by dawehner, damiankloip, Wim Leers: Fixed A Drupal 8 AjaxResponse that must return a 403, returns a 403 and prints 'A fatal error occurred: '

Issue #2309889 by tim.plunkett, dawehner: Fixed DrupalKernel requires a Drupal\Core\*\Plugin directory for annotated classes to be discovered.

Issue #2337927 by effulgentsia, plach, fago: Fixed SqlContentEntityStorage::onFieldStorageDefinition(Create|Update|Delete)() is broken for base fields.

Issue #2329847 by tuutti, rachel_norfolk, Cottser | davidhernandez: Use Attribute to replace hard coded classes in language-negotiation-configure-form.html.twig.

Issue #2325571 by asif_khan, omers | dawehner: Replace _theme() calls by calls to \Drupal::theme()->render().

Issue #2334785 by znerol: Remove _maintenance request attribute from SpecialAttributesRouteSubscriber.

Issue #2303525 by paulmckibben, tim.plunkett: Provide link tags to alternate languages (hreflang) in HTML head.

Issue #2337227 by er.pushpinderrana, larowlan: Fixed NodeAccessControlHandler performs non-strict in_array check.

Issue #1976298 by larowlan: Move taxonomy_get_tree() and associated functions to Taxonomy storage, deprecate procedural wrappers.

Issue #2321609 by benjy, dawehner: Fixed Provide a helpful message in case requirements are not met.

Issue #2337847 by alexpott, YesCT, martin107: The negotiated method_id does not need to be sorted on the Language or ConfigurableLanguage object.

Issue #2328411 by dawehner, geerlingguy, herom: Convert all permissions to yml files and permission callbacks.

Issue #2337859 by martin107 | YesCT: LanguageUrlRewritingTest should not be setting the id of a language.