Modified _to_format_dct and _from_dict_to_object of
Deg2QsrsElement, Deg2ModularFormQseries,
SymmetricWeightGenericElement, SymmetricWeightModularFormElement.
minor fix.
added __gt__, __lt__ to PrecisionDeg2.
Modified save_basis_as_binary, load_basis_from of KlingenEisensteinAndCuspForms.
Use PrecisionDeg2.
Modified __init__ of KlingenEisensteinAndCuspForms, CuspFormsDegree2.
Modifid group_by_reduced_forms_with_sgn.
Minor fix.
Added test_group_by_reduced_forms_with_sgn.
Added test_odd_mul.