Violence at SF nightclubs has been all the rage this year - all nine days, that is - and now a summit is being held this month in order to curb the violent tomfoolery. A few choice incidences to refresh your memory: Marcus Pepper, 26, was killed on New Year's Day outside a Ninth Street warehouse SOMA party; Clarence Corbin 34, was shot outside Jelly's Dance Cafe in Mission Bay; Club Vessel was, well,......