An accused squatter from hell could actually have a claim to the rent-controlled pad in a swanky West Village building where he’s allegedly been terrorizing neighbors for months, legal experts said. Melvin DeJesus, 66, moved into the 5th-floor unit at 400 Bleecker St. roughly two decades ago when a lifelong New Yorker with a “heart of gold,” John Grafenecker, took him in, a close relative of the late tenant said. “John really took care of Mel no matter what — he paid a lot of bills, food, Con