A Randomised, Double-blind, Parallel Group Study to Assess the Efficacy and Safety of 52 Weeks of Once Daily Treatment of Orally Inhaled Tiotropium + Olodaterol Fixed Dose Combination (2.5 µg / 5 µg; 5 µg / 5 µg) (Delivered by the Respimat® Inhaler) Compared With the Individual Components (2.5 µg and 5 µg Tiotropium, 5 µg Olodaterol) (Delivered by the Respimat® Inhaler) in Patients With Chronic Obstructive Pulmonary Disease (COPD). [TOnado TM 1]