That annoyance no longer seems to matter, so great is the hunger for buildable lots in Fishtown and the many emerging subsets of Kensington - South, East, Somerset, Old Richmond. In defiance of the laws of physics and real estate, the homey Front Street Cafe set up shop last year on the corner of Thompson Street, a few steps from the El. This spring, a high-end Italian restaurant did it one better: After embedding itself in the shell of the former Wm. Mulherin's Sons whiskey merchant, the owners put out sidewalk tables. Even with that extra seating, reservations are still hard to come by.