Implement Editor for UML Class-Diagram

As a Business Analyst or System Designer I would like to create or update UML Class-Diagrams and store it immediately in a semantic net using the SpecIF.
Idea: Use [diagram-js](https://github.com/bpmn-io/diagram-js), an online diagramming library upon which bpmn-io [(Demo)](https://demo.bpmn.io/bpmn) is built.