The redamber leaves and blue skys, not to mention the crescent moon made it a beaut of a fall weekend.  It was a parade of costume colors on the 60 dancers Virsky Ukrainian National Dance today in a sold out performance. Famous classical choreographers have been guilty of plagiarizing Slavic, Gypsy and Ukrainian folk dance and diluting it for commercial audiences in the West. It is always instructive to know the difference, and get to see the authentic artistry at foot.   Among its spectrum of artistry, Virsky’s dance acrobats is pretty damn spellbinding accented with those dervish turns, horizonal body whips and explosive vaults. But the move that still gets them are those arms- folded bent- knee Cossack kickouts.