Improve the Inheritance Hierarchy of Generated Domain Models

[sgarfinkel]

Given a ResourceShape Foo, the following are generated:

public class Foo extends AbstractResource implements IFoo {
...
}

public interface IFoo {
...
}

This inverts the standard Java pattern where the interface should define all contracts that must be implemented by the underlying concrete classes (including other interfaces) so that you can use the interface interchangeably with the underlying datatype when possible.

Instead, the generated interface should also extend IExtendedResourceShape:

public interface IFoo extends IExtendedResourceShape {
...
}

[jadelkhoury]

Sound reasonable. The main reason I introduced interfaces was to implement multiple inheritance, which was needed for very specific use cases in Lyo Designer.
So we need to test this suggestion in those scenarios when FOO extends ResourceA, but also implement IResourceB and IResourceC