Thirty-one years and counting, and the Terminators keep rolling off the assembly line like new iPhones. They are upgraded with shape-shifting abilities, rebooted Sarah Conner assassination levels and, one presumes, better selfie cameras. “Terminator Genisys,” directed by Alan Taylor (“Thor: The Dark World”), is the fifth entry in the series begun by James Cameron and a naked money grab aimed at rejuvenating a flagging franchise.