A 52-Week International, Multi-centre, Randomised, Parallel-group, Double-blind, Active-controlled, Phase III Study With a 156-Week Extension Period to Evaluate the Efficacy and Safety of Dapagliflozin in Combination With Metformin Compared With Sulphonylurea in Combination With Metformin in Adult Patients With Type 2 Diabetes Who Have Inadequate Glycaemic Control on Metformin Therapy Alone.