Brain should allow selection of an atlas & display the parcel names on hover (e.g., in the status bar) even when show_traces=False

[hoechenberger]

We were looking at "static" data (only a single time point), hence we turned off show_traces to have more space. But then when we discovered an "interesting" region, we couldn't figure out the name of the parcel without restarting Brain with show_traces=True, because only then the Annotations dropdown will appear.