Issue #1754246 by webflo, swentel, penyaskito, andypost, alexpott, YesCT, dagmar: Languages should be configuration entities.
Issue #1498674 by plach, das-peter, Schnitzel, dawehner, YesCT, attiks, Berdir, Gábor Hojtsy, Soul88, Carsten Müller: Refactor node properties to multilingual.
Issue #1620010 by dawehner, ParisLiakos, plach, jibran: Move LANGUAGE constants to the Language class.
Issue #1818556 by das-peter, plach, fago, Berdir, vijaycs85: Change notice: Convert nodes to the new Entity Field API.
Issue #1885868 by larowlan, swentel, Berdir: Fixed NodeRevisionsTest.php contains two classes, not PSR-0.
