"What did you do on your summer vacation?" is a big conversation starter this time of year  Dancers dance, whether on tour, as featured guests at festivals, or for members of American Ballet Theatre, exploring their art at  Co•Lab Dance .  Led by Founder-Director and ABT colleague  Lauren Post, On September 6 and 7, Co•Lab showed two sold-out audiences at Manhattan Movement & Arts Center what they did between ABT's two seasons at Lincoln Center.  The four engaging new works were created by female choreographers; something their home company is seriously trying to address.  Here this was a matter-of-fact new normal. Forming Co•Lab''s sophomore company were ABT Soloists