Crystal structure of poly[diaqua-bis(µ2-thiophene-2,5-dicarboxylate-κ2O:O')(3,5-di(1H-imidazol-1-yl)pyridine-κ2N:N')cobalt(II)], Co(H2O)2(C6H2O4S)(C11N4H9), C17H15CoN5O6S