Revert "Issue #1475510 by timmillwood, hussainweb, davidwbarratt, Mile23, pfrenssen, claudiu.cristea, webchick, Crell, catch, patcon, RobLoach, dawehner, sun, kim.pepper, gagarine, effulgentsia, drumm, katbailey, Sylvain Lecoy, Mixologic, jhedstrom: Remove external dependencies from the core repo and let Composer manage the dependencies instead"

This reverts commit c6c69134.

Issue #2571539 by Lendude, Surabhi Gokte, Cottser, swentel, emma.maria, alexpott, Manjit.Singh: Progress bar higher than progress track

Issue #2651766 by eojthebrave, malavya, jhodgdon, alexpott: Update link in documentation block for t() function

Issue #2578173 by Peacog, maximpodorov, marvin_B8, andypost, alexpott, tatisilva: Increase menu title maxlength to 255 in forms containing menu items

Issue #2641540 by Mac_Weber: Replace deprecated usage of  entity_create('entity_test_mulrev') with a direct call to  EntityTestMulRev::create()

Issue #1475510 by timmillwood, hussainweb, davidwbarratt, Mile23, pfrenssen, claudiu.cristea, webchick, Crell, catch, patcon, RobLoach, dawehner, sun, kim.pepper, gagarine, effulgentsia, drumm, katbailey, Sylvain Lecoy, Mixologic, jhedstrom: Remove external dependencies from the core repo and let Composer manage the dependencies instead

Issue #2587337 by sdstyles: hook_node_links_alter() names its parameters differently from its implementations

Issue #2649602 by hchonov: hook_translation_create is not invoked with the new entity translation but with the previous entity object

Issue #2500525 by dawehner, catch, pjonckiere, mpdonadio, Wim Leers, jhodgdon: Time ago/hence date/time formatting breaks caching; needs appropriate max age or javascript

Issue #1232572 by deviantintegral, joachim, cweagans, kenorb, bleen, webflo, ceng, Elijah Lynn, sriharsha.uppuluri: Add a variable to disable fixing file permissions in drupal_install_fix_file()

Issue #2351919 by almaudoh, Wim Leers, claudiu.cristea: Replace uses of drupal_get_path() with __DIR__  or Extension::getPath() where possible

Issue #2489472 by cilefen, amateescu, bircher, saki007ster, swentel, andypost, alexpott, Bojhan: Field-based module dependency uninstall message is unhelpful and not grammatically correct

Issue #2559241 by droplet, tic2000: Closing an #ajax dialog triggers Javascript errors when scrolling

Issue #2392057 by tim.plunkett, vasi, benjy, alexpott, Gábor Hojtsy, YesCT: Config schema fails to expand dynamic top-level types

Issue #895656 by smccabe, adinac, andypost, mfb: dom and hash extensions already required by system module, do not need to be required by simpletest

Issue #2660026 by theMusician: Remove obsolete \Drupal\Core\Config\Entity\ConfigEntityBase::$pluginConfigKey

Issue #2659078 by dpi: Unexpected access operation throws exception when node grant system is active

Issue #2528420 by cane989, andrewmacpherson, malavya, mgifford, Shabbir, Denchev, Cottser: Two H1's in Installation Process

Issue #2442721 by daffie, mgifford: Direct access to the variable $parent in Drupal\Core\Field\FieldItemBase::getLangcode()

Issue #2633308 by dawehner, mparker17, Wim Leers, Fabianx: Views cache contexts are lost (and thus do not bubble) when rendering a view's block display

Issue #2553553 by burkeker, alvar0hurtad0, meramo: Remove references to system.module.css and system.theme.css in core