After the success of 2013’s low-budget horror thriller The Purge, followed the next year by The Purge: Anarchy, it was inevitable that there would be more in this clever, diabolically cynical and violent series of films that are made for modest cost, but produce big returns. The Purge: Election Year, a timely title if ever there was one, is the most entertaining of the bunch, and with voter dissatisfaction at an all-time high, you have to think that moviegoers just may be…