Cuts a striking figure in a Johnny Cash-like ensemble of black boots, black jeans, black shirt and black overcoat, but Ravi DeRossi remains enough of an unknown that customers pay no attention to him as he gives a tour of his various bars in the East Village. There are a lot of bars, by the way. Over the course of a decade or so, Mr. DeRossi, 42, has quietly, quirkily built up an empire of 15 drinking establishments and restaurants in downtown