Think the only way to see a big-screen movie is while slurping a 64-oz. soft drink, eating a five-dollar candy bar and shushing the wannabe film critic behind you? That’s not the case anymore, thanks to people like John Young, part of a loosely knit network of celluloid renegades resurrecting the drive-in for a new age. For the past four years or so, the 38-year-old Web developer has been showing films — real, honest-to-goodness 16mm film — from a 1970s school projector mounted on the sidecar of his 1977 BMW motorcycle.