Issue #2152203 by joelpittet, InternetDevels, rteijeiro,  steveoliver, hussainweb, shanethehat, jenlampton, kpa, AnythonyR, EVIIILJ, kgoel, Cottser, dsdeiz, hanpersand: Convert theme_container() to Twig.
Issue #2152211 by joelpittet, IshaDakota, rteijeiro, steveoliver, hussainweb, shanethehat, jenlampton, kpa, AnythonyR, EVIIILJ, kgoel, Cottser, dsdeiz, hanpersand: Convert theme_form() to Twig.
Issue #2152209 by longwave, joelpittet, steveoliver, hussainweb, shanethehat, jenlampton, kpa, AnythonyR, EVIIILJ, kgoel, Cottser, dsdeiz, hanpersand: Convert theme_fieldset() to Twig.