Students at New York University, where a year of undergraduate education can run to about $66,000 in room, board, tuition and fees, often complain about the cost of four years at the school in Greenwich Village.  Now, N.Y.U. has a suggestion for them: Finish faster.  On Friday, the university announced a series of measures that make it easier to graduate in under four years, part of an initiative aimed at diminishing the university’s enormous affordability problem.