Issue #2175765 by alexpott, Gábor Hojtsy: Fix comment in system_theme_default() to not refer to obsolete function

Issue #1979468 by Wim Leers, nod_, pwolanin, longwave, thedavidmeister, jessebeach, larowlan | catch: .active from linkGenerator(), l() and theme_links() forces an upper limit of per-page caching for all content containing links.

Issue #2136507 by Wim Leers: Use client-side cache tags & caching to eliminate 1 HTTP requests/page for rendering Contextual Links.

Issue #2175017 by tim.plunkett, yched: FieldDefinition::create() doesn't populate default 'settings' for the field type.

Issue #2168333 by tim.plunkett, EclipseGc, yched, fago: Ensure custom EntityType controllers can be provided by modules.

Issue #2102489 by webwarrior, InternetDevels: Remove drupal_set_title in views module controllers (last instance of drupal_set_title()).

Somehow this broke PHPUnit, so rolling back for now.

This reverts commit 91b465bd.

Issue #1862202 by plach, Berdir, katbailey, ParisLiakos, alexpott, chx, sun, larowlan, Gábor Hojtsy, cosmicdreams, vijaycs85, YesCT, penyaskito, andypost, Albert Volkman, joelpitett: Objectify the language system.

Issue #1649780 by effulgentsia, jibran, Wim Leers, nod_, hefox, joelpittet, kaare, BarisW, sun, rbayliss, Cottser, fubhy: Remove first/last/odd/even classes in favor of CSS3 pseudo selectors.

Issue #2164597 by longwave, StephaneQ, emok: Doxygen @return tag missing for drupal_render_children.

This caused a conflict in the language objectification patch. Postponing.

This reverts commit 9e017ada.

Issue #2161763 by Wim Leers, sun: Remove unnecessary drupalSettings.editor.getUntransformedTextURL setting.