The 32-year-old Portuguese international shall don the Red and White stripes of Sourav Ganguly co-owned team. Atletico de Kolkata have announced on Wednesday Helder Postiga as their marquee signing for the second edition of Indian Super League (ISL). Last season Postiga plied his trade for Deportivo La Coruna in Spain where he scored just once in 14 matches. He has played for the likes of Valencia, Lazio, Real Zaragoza, Sporting CP, Tottenham and Porto as…