Issue #2224761 by Gábor Hojtsy, alexpott, pfrenssen, effulgentsia, xjm, mlncn: Add a generic way to add third party configuration on configuration entities and implement for field configuration.
Issue #2326719 by plach, effulgentsia: Move pseudo-private table mapping functions from ContentEntityDatabaseStorage to public API of DefaultTableMapping.
Issue #2273277 by Wim Leers, effulgentsia, Fabianx: Fixed Figure out a solution for the problematic interaction between the render system and the theme system when using #pre_render.
Issue #1966436 by follow-up by sun: Move tests to proper directory.
Issue #2037979 by Gábor Hojtsy, Sweetchuck, jhodgdon, dawehner: Fixed 'Current user's language' views filter label is named very misleading.
Issue #2309671 by herom: Fixed admin configuration page RTL CSS.
Issue #2315459 by herom, seiplax: Fixed RTL for config translation form.
Issue #2246679 by YesCT, alimac, Michelle, martin107, eugenesia: Make Language module's LanguageInterface (to be ConfigurableLanguageInterface) extend Core's LanguageInterface.
Issue #2330043 by andypost: Theme handler is not needed for theme manager.
Issue #2329653 by znerol: Remove left over abstract class PathListenerBase.
Issue #2202185 by Wim Leers, effulgentsia, msonnabaum, damiankloip, alexpott: Statically cache Role entities to speed up (User|UserSession)::hasPermission().
Copy the Composer files to the core directory.