SEOUL (Reuters) – South Korean rapper Psy plans to follow his "Gangnam Style" YouTube megahit with a single called "Gentleman" and a new dance, but is playing coy about everything else ahead of the song's release, which was moved up a day to April 12. The song will be available for Korean fans then, but Psy will perform it in public for the first time at an April 13 concert. "The new song is extremely fun and … what I can tell you is the song title is 'Gentleman'", Psy told local television late on Monday. …