Issue #2652850 by tstoeckler, mohit_aghera, idebr, hchonov, mbovan,...

Issue #2652850 by tstoeckler, mohit_aghera, idebr, hchonov, mbovan, rodrigoaguilera, jwilson3, pguillard, espurnes, dravenk, ainarend, handkerchief, alexpott: Title for details form elements is not set as '#markup' and it will be escaped, but all other form elements use '#markup' and are not escaped