Issue #2407733 by mortendk, rteijeiro, sivaji@knackforge.com: Remove classes from system templates i*.html.twig

Issue #2349759 by davidhernandez, mortendk, rteijeiro, harish86, Sumit kumar, saki007ster, Mukeysh, brahmjeet789, nitishchopra, falkendk, Maninder, Vidushi Mehta, Ashish sandil, jitendra verma, crowdcg, sivaji@knackforge.com, dernetzjaeger: Copy system templates to Classy.