It’s said that a city – a city like Toronto, say – whose boosters often rely on the adjective “world-class” to describe both its overall grooviness and its particular charms can’t, in fact, be truly world-class. You’re either world-class or you’re not and no amount of huffing, puffing or tub-thumping is going to grant a burg that cachet. World-class, in short, is self-evident and unspoken. Still, you can’t keep a person from thinking something’s world-class. Which is, in fact, what I was thinking one cool, overcast morning last week while touring the Aga Khan Museum with educational consultant Patricia Bentley. The museum, which opens Thursday [September 18th] (a ceremonial opening, featuring Prince Shah Karim Al Hussaini Aga Khan, was held Sept. 12), has been a long time coming, Toronto having been named its home 12 years ago this October by the prince, spiritual head of the planet’s 15 million Shia Imami Ismaili Muslims.