You never saw a guy in Dockers move like this. Pleated Dockers. Frontman Samuel T. Herring bounded and pogoed across the stage like a gymnast. He bent at the knees and the waist and pointed at audience members and looked them straight in the eye and generally danced like a man overcome throughout Future Islands’ sold-out set of baroque, romantic new-wave dance-pop Tuesday night at Bottom of the Hill. It was a sight to see.