The Red Sox have never lacked for colorful characters, but leave it to Dennis “Oil Can” Boyd to make the likes of Bernie Carbo, Carl Everett, and Manny Ramirez seem like regular guys, without much in the way of issues. The same cannot be said for the Can, as any reader will discover just a few pages into “They Call Me Oil Can,” his memoir that doubles as a scream of pain into the abyss.