A stranger shoved an 86-year-old woman to the ground — breaking her teeth — in a random attack near the exit of an Upper East Side supermarket over the weekend, cops said. The victim was leaving Morton Williams on Third Avenue near East 63rd Street around 1:25 p.m. Sunday when the maniac suddenly pushed her from behind, authorities said. The force of the shove sent the senior face-first into a pole supporting scaffolding set up outside the store, the sources said. The blow left her with multiple broken teeth, as well as injuries to her left eye and back, cops...