Issue #2942907 by plach, amateescu, Berdir, tim.plunkett, hchonov,...

Issue #2942907 by plach, amateescu, Berdir, tim.plunkett, hchonov, gabesullice, jibran, xjm, tedbow, timmillwood, larowlan, Sam152, pmelab, catch, effulgentsia: Entity system does not provide an API for retrieving an entity variant that is safe for editing