Carbodiimide-mediated Annelation of a [1,2,4]Triazole Ring into a Heterocyclic Ring: Synthesis of [1,2,4]Triazolo[4,3-b]triazole, Imidazo[1,2-b][1,2,4]triazole and [1,2,4]Triazolo[1,5-d][1,2,4]triazine Derivatives