LONDON (Reuters) - The Spice Girls hit the red carpet in London on Tuesday for the world premiere of a musical based on their meteoric rise to fame in the 1990s, and will discover if "Girl Power" still appeals to the next generation. "Viva Forever!" opens at the Piccadilly Theatre with a star-studded launch including all five members of the band, and hundreds of die-hard fans are expected to block the streets to get a glimpse of the girls who once ruled the charts. ...