Bournonville training creates some of the most elegant male dancers in the ballet world. Their upper bodies seem to move with poise, ease and a mix of strength and lightness, no matter what sort of footwork is going on underneath. This was especially evident last night at the Royal Danish Ballet's performance in Lincoln Center, when a couple dozen or so of the company's men danced Bournonville Variations, a mash-up of traditional classroom exercises created by the other Mr. B.