BACK in the 1970s, a gutsy blonde named Jill Freedman armed with a battered Leica M4 and an eye for the offbeat trained her lens on the spirited characters and gritty sidewalks of a now-extinct city. Her New York was a blemished and fallen apple strewn with piles of garbage. Prostitutes and bag ladies walked the streets, junkies staked out abandoned tenements, and children played in vacant lots.