“Regina Spektor: Live in London” — that’s what it’s called, and that’s what you get. Eighteen songs, performed in December 2009 at the Hammersmith Apollo, with an absolute minimum of onstage chatter and dollops of stylishly grainy, MTV-like filler: Ms. Spektor on the plane from New York, driving through London, applying makeup before the show. It’s perfectly tasteful, a fine showcase for her music and, more important, a fine promotional tool for the accompanying CD and DVD (which — surprise — co...