“Troubled” does not begin to describe the history of the Chicago theatre recently known as the Shubert (now renamed for a corporate sponsor.) “Producers coveted it for its scale, which is similar to Broadway houses, but many theatergoers groaned at the thought of an evening at the 100-year-old Shubert, with its drab colors, its paucity of bathrooms and its congested, claustrophobic bottleneck of a lobby.” But a $14 million renovation has not only opened the theatre up, it has revealed some striking architectural details not seen since the building’s earliest days.