If you’re not sure whether Mark Morris’ Acis and Galatea is opera or dance or theater or what, then you’re probably on the right track. “That’s historically accurate,” said Mark recently on the phone, pointing out that in the Baroque “opera included all of those things: That’s the whole point.” The choreographer’s extravagant new production of Acis, Handel’s masterpiece drawn from Ovid’s Metamorphoses and performed here February 6th and 7th on the Harriman-Jewell Series, constitutes one of the most auspicious assemblages of talent that Kansas City has ever seen on a stage.