Crystal clear as leaders Leicester march on

By Martyn Herman LONDON (Reuters) - Indomitable Leicester City stayed bang on course for the Premier League title as Riyad Mahrez scored the only goal at Crystal Palace on Saturday to open up an eight-point lead with seven games left.     Third-placed Arsenal, 11 points behind with a game in hand, made a timely return to form with a 2-0 win at Everton and Tottenham Hotspur can reduce the gap to five on Sunday.     But any hopes that the two London rivals and fourth-