Boston city councilors Friday sharply questioned an NStar official over two power outages in recent weeks, with council president Stephen Murphy calling for outside inspections of the power company’s facilities. “I think it’s just crazy you’re self-policed,’’ Murphy said at a hearing on the outages this morning. The massive outage in the Back Bay in March, followed by a brief outage earlier this month, showed that “not enough is being done,’’ he said.