add internal comparison method
add CgVar copy method
fix CgVar_Instance()
implemented the following methods:
Cgvar.__eq__
CgVar.__ne__
CgVar.__lt__
CgVar.__gt__
CgVar.__le__
CgVar.__ge__
CgVar.__copy__
Cvec.__add__
Cvec.__iadd__
Cvec.__copy__
Cvec.__deepcopy__
Cvec.index
Cvec.remove