Rahm Emanuel, Chicago’s mayor-elect, signaled his intent to “raise up” the arts in Chicago, especially in the neighborhoods, and previewed a major generational and cultural shift at a City Hall about to be run by a confident leader who listens to the alternative rock band Wilco, likes the darker plays at Steppenwolf Theatre and American Theater Company and is not about to stop hanging out at rock venues like Schubas or the Riviera Theatre.