Bayer Leverkusen have added the German Cup title to their Bundesliga triumph and completed their maiden domestic double with a 1-0 win against second division team Kaiserslautern on Saturday. Granit Xhaka scored the winner in the 16th minute with a stunning long-distance shot after a sloppy clearance from the Kaiserslautern defence. “I’m proud and happy for the players. It’s completely deserved,” Leverkusen coach Xabi Alonso said. “Tonight I will drink a German beer.” Leverkusen midfielder Robert Andrich said it was a “great, great feeling,” to lift the trophy. “This moment, when you lift the …