__eq__ methods in opa and mdb

[HajimeKawahara]

I would define eq methods (and neq ) in ExoJAX classes to enable to use == (and !=) operators.

• [x] opa
• [x] mdb

The use of the comparison of __dict__ (the following code) did not work:

    def __eq__(self, other):
        if isinstance(other, MyClass):
            return self.__dict__ == other.__dict__
        return False

So, we decided to compare the attributes directly.

[HajimeKawahara]

done by #512