Rona Davis had a dream and left her dusty job as some kind of assistant in the city to pursue it. The child of Guyanese immigrants, Davis is a lifetime striver and sits pleasantly, amicially inside her debut creation: a now year-old, 60-seat bistro on Knickerbocker Avenue called, with relieving frankness, 191 Knickerbocker. It is, perhaps, this side of Bushwick’s only real major thoroughfare. The restaurant is situated a few blocks shy of Maria Hernandez Park, a little past the flurrying bustle of discount retailers and closer to the rarely occupied record store that also sells graphic novels.