Support dictionary semantics in EA class

[onitake]

The objects.EA class is somewhat awkward to use, because it only has custom get() and set() methods, in addition to the custom serializer from_dict()/to_dict().

It would be very useful to add the full set of collection operations, as described in https://docs.python.org/3/reference/datamodel.html#emulating-container-types , or inherit from https://docs.python.org/3/library/collections.html#collections.UserDict and extend as needed.

[sarya-infoblox]

Hi @onitake, we will have a look into this and will update you