Ditto Thing Descriptions

[Eclipse Ditto](https://eclipse.org/ditto/)™ is a technology in the IoT implementing a software pattern called “digital twins”.
It recently added integration for Web Of Things, details of this integration can be found [here](https://www.eclipse.org/ditto/basic-wot-integration.html).
I think it is an important point to make Thing Descriptions generated by Ditto also working in thingweb.node-wot.
Looking at the implementation, i think that the problem could be in the fact that [Ditto Features](https://www.eclipse.org/ditto/basic-feature.html) are allocated in an external TD.