An Improved Large-Scale (90 g) Synthesis of Bis(tetraethylammonium)bis(1,3-dithiole-2-thione-4,5-dithiol)zincate: Synthesis and X-ray Crystal Structures of Bicyclic and Tricyclic 1,4-Dithiocines Derived from 1,3-Dithiole-2-thione-4,5-dithiolate (DMIT)