A troubled exotic dancer who recently separated from her wife and lost her kids to foster care was gunned down execution style on a Gramercy Park sidewalk early Thursday, cops and witnesses said. Imani Armstrong was headed home from a late shift at her other job at an IHOP at about 5 a.m. when a masked gunman snuck up and blasted her in the back of the head at East 14th Street and Irving Place... The motive for the slaying remained unknown, but the shooting of was not random, cops said. “The individual was targeted,” Chief of Department Kenneth Corey...