One of them was "slightly pretty," so the freelance film director decided to say hi. Next thing he knew, he was encircled, beaten and knifed in the gut right there on a Greenwich Village sidewalk - by seven bloodthirsty young lesbians. "The girls started coming out of nowhere," Dwayne Buckle told a Manhattan jury yesterday, describing the bizarre beat-down he suffered last summer, allegedly at the hands of a seething sapphic septet from Newark, N.J. "I felt like I was going to die." Buckle, 29, of Queens, took the stand in Manhattan Supreme Court yesterday to admit he was defenseless...