Issue #1825952 by Fabianx, joelpittet, bdragon, heddn, chx, xjm, pwolanin, mikey_p, ti2m, bfr, dags, cilefen, scor, mgifford: Turn on twig autoescape by default

Issue #2188523 by sun: ExceptionController does not respect configured system.logging:error_level (verbose backtrace).

Issue #2176105 followup by sun: Installer catches exceptions and manually re-prints them; does not use error/exception handler.