X-ray crystal structures of the 1,3,2-benzodithiazolyl dimer and 1,3,2-benzodithiazolium chloride sulfur dioxide solvate: comparison of the molecular and electronic structures of the 10-.pi.-electron C6H4S2N+ cation and the C6H4S2N.bul. radical and dimer and a study of the variable-temperature magnetic behavior of the radical