[Codeplex feature $448] Support Complex Type Inheritance In Web API

ODL Spec says:

A complex type can inherit from another complex type by specifying the
QualifiedName of the base complex type as the value for the BaseType
attribute.

In Web API, the entity type inheritance is already supported but the complex type inheritance not supported.

Therefore, this feature requires to support the complex type inheritance
and integrate the implementation between the entity type inheritance and
complex type inheritance.

Thanks.