Issue #2447727 by webflo, quietone, jofitz, Neslee Canil Pinto, mradcliffe, claudiu.cristea, k4v, yogeshmpawar, kgoel, dimaro, hussainweb, vprocessor, malcomio, iMiksu, phenaproxima, keithm, tlyngej, benjy, heddn, infopicard, Kristen Pol, KarenS: Add base class for migrating reference fields

Issue #2369119 by Lendude, olli, mpdonadio, alexpott, dagmar, mikeker, vprocessor, tlyngej, rakesh.gectcr, herved, Blanca.Esqueda, lomasr, anavarre, tacituseu, ronaldtebrake, aleevas, dawehner, Grayside: Fatal error when trying to save a View with grouped filters using other than string values

Issue #1987848 by disasm, ocsilalala, kim.pepper, pwieck, Cottser, pratik60, h3rj4n, pfrenssen, InternetDevels, ParisLiakos, rgoodine, tlyngej, vijaycs85, robeano: Convert system_theme_default() to a new style controller.