Schema definitions should generated Java pojos regardless if they are referenced

[ddcruver]

The use case is that I have a type that uses an interface, defined outside of jsonschema2pojo, because jsonschema2pojo doesn't support generating of interfaces. I then attach a property with that interface as its type. I then define implementations of that interface in the definitions section, possibly not even in the same schema file.

I would like it to generate theses classes but it does not because no top-level object as defined by a schema file references them directly.