Issue #1938926 by sun, Cottser, joelpittet, pplantinga: Convert simpletest theme tables to table #type.

This reverts commit ae8be3cc.

This reverts commit 06e6e923.

Issue #2175459 by sun: Convert Drupal\system\Tests\InstallerTest into a new Drupal\simpletest\InstallerTestBase.

Issue #2140433 by pwolanin, chx, Owen Barton, dstol, Heine, Damien Tournoud: Port SA-CORE-2013-003 to Drupal 8.

Issue #2044367 by InternetDevels, Berdir, wildflower_0002, ianthomas_uk, ParisLiakos, Xano | cosmicdreams: Replace calls to lock() with \Drupal::lock().

Issue #2070369 by herom, bdgreen, Mac_Weber, InternetDevels, sidharthap, JeroenT: Remove all calls to deprecated function language().

Issue #2195933 by Sam152: 'Back to site' button doesn't work when the user originates from the homepage.

Issue #924322 by tim.plunkett, Devin Carlson, dicix, mike stewart | Jeff Burnz: Color_scheme_form_submit() assumes color.inc provides keys that should be optional.

Issue #2156853 by olli, quicksketch: Views UI Save and Cancel buttons break existing locks by other users.

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

Issue #2191911 by Xano: Improve @param and @return variable types for \Drupal\Core\Config\ConfigFactoryInterface.

Issue #1810178 by sidharthap, swentel, Xano, Rajesh Ashok, David Hernández, durifal, yched, guy_schneerson: _field_info_collate_fields() is not language-aware, may return wrong values.

Issue #1851234 by alexpott: Slow yaml parsing slows down tests which load/save many config files (e.g. views).

Issue #2199483 by damiankloip, alexpott: Provide a default config_prefix based on entity type ID and provider.

Ugh. Some more cache() calls have sneaky-sneaked in.

This reverts commit 4dbdfeeb.

Issue #2186115 by chakrapani, longwave, jhodgdon, benjy, chrischinchilla, swentel: Shortcuts are added with no link title (hence unusable).