Issue #1728804 by Berdir: Introduce (Content)EntityDeleteForm and children to handle entity deletions

Issue #2143729 by tstoeckler, plach, jsbalsera, Berdir, mauzeh, damiankloip, andypost: Entity definitions miss a language entity key

This reverts commit 3ac426f9.

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

Issue #216064 by Xano, idflood, drifter, Artusamak, ygerasimov, sun, ParisLiakos, Cottser, TravisCarden, marcingy, floretan, catch, tedbow: Entity form "Delete" button triggers server-side + HTML5 form validation; change "Delete" button to a link.

Issue #2074037 by Wim Leers, effulgentsia: Add drupalPostUrl() — drupalPost()/drupalPostAjax() are for forms only, D8 JS performs non-form HTTP requests.

Issue #2057869 by dawehner, jibran: Provide an alias for 'plugin.manager.entity' called 'entity.manager'.

Issue #1620010 by dawehner, ParisLiakos, plach, jibran: Move LANGUAGE constants to the Language class.

Issue #1833334 by das-peter, plach, Berdir, fago: EntityNG: integrate a dynamic property data table handling.

Issue #1696640 by fago, effulgentsia, tim.plunkett, dixon_, plach: Add a uniform Entity Property API.