MANCHESTER, England, Jan 17 : Arsenal took a seven-point lead at the top of the Premier League after a scoreless draw with Nottingham Forest on Saturday following an exhilarating 2-0 derby victory for Manchester United that dealt a devastating blow to Manchester City's title hopes.  Arsenal could have gone nine points clear with a win at Forest, but Sean Dyche's side fought tooth and nail to secure the draw, becoming only the second team to prevent Mikel Arteta's side from scoring in the