Next week, Kate Kraczon begins her new job as chief curator of the Montclair Art Museum. Founded in 1914, the New Jersey institution was among the first in the country to organize itself around American art, an area of study that now affords many opportunities. Kraczon, who arrives from the David Winton Bell Gallery at Brown University, takes over a post held since 1994 by Gail Stavitsky, and joins incoming director Todd Caissie at a moment of b…