Issue #2546618 by plach, dawehner, chx, bojanz: Replace the Symfony Translation component with a custom interface since we don't use it

Issue #2343035 by fago, dawehner, larowlan, ianthomas_uk, cilefen, hussainweb, Miroling, jibran, beejeebus, dashaforbes, webmozart, klausi: Upgrade validator integration for Symfony versions 2.5+