TRIPOLI (Reuters) -Libyan protesters will keep demonstrating until all the ruling elites quit power, they said on Saturday, after rallies in most main cities on Friday culminated in a crowd storming the parliament building and torching parts of it. The protest movement said it would step up its campaign from Sunday, urging demonstrators to set up tents in city squares and practise civil disobedience until they achieve their goal of ousting political institutions and holding new elections. Security vehicles surrounded government buildings in the capital after sunset on Saturday and there was no…