Issue #2559605 by Cottser, stefan.r: Convert SafeMarkup::checkPlain() in render arrays to #plain_text

Issue #2457887 by prateekMehta, stefan.r, rpayanm, alexpott: Use Utility\SafeMarkup class instead of Utility\String for placeholder(), checkPlain(),format() functions

Issue #2432837 by Wim Leers, Fabianx: Make cache contexts hierarchical (e.g. 'user' is more specific than 'user.roles')

Issue #2446995 by tim.plunkett, Berdir: Block content titles are not escaped on new block form (Port SA-CONTRIB-2013-082)

Issue #2329101 by Wim Leers: CacheableInterface only has a getCacheKeys() method, no getCacheContexts(), leads to awkward implementations

Issue #2318437 by Wim Leers, Gábor Hojtsy, geertvd: Replace the hardcoded langcode key on blocks with the 'language' cache context

Issue #2347999 by Mile23, daffie, cs_shadow, cosmicdreams: DrupalUnitTestBase is deprecated, replace with KernelTestBase

Issue #2339151 by EclipseGc, tim.plunkett, Gábor Hojtsy, effulgentsia: Conditions / context system does not allow for multiple configurable contexts, eg. language types

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

Issue #697760 by sun: Replace getInfo() in tests with native phpDoc + annotations (following PHPUnit).

Issue #2278541 by tim.plunkett, kim.pepper, Bojhan, EclipseGc: Refactor block visibility to use condition plugins.

Issue #2158003 by Wim Leers, msonnabaum, effulgentsia, moshe weitzman: Remove Block Cache API in favor of blocks returning #cache with cache tags.

Issue #2195753 by tim.plunkett: Changes to config entities that use plugins are not propagated to the plugins.

Issue #1956448 by benjy, tim.plunkett, ed.hollinghurst, YesCT: Use the block instance title on the block admin listing.

Issue #2022897 by dawehner, sdboyer, tim.plunkett: Shift responsibility for creating unique config id/machine name off of (views) block plugins and onto BlockFormController.

Issue #1872876 by chx, fubhy, dawehner, alexpott, tim.plunkett: Turn role permission assignments into configuration.

Issue #1927608 by EclipseGc, tim.plunkett, effulgentsia: Remove the tight coupling between Block Plugins and Block Entities.