jBPM5Extensions.ecore was originally copied from here:

https://github.com/droolsjbpm/jbpm/tree/master/jbpm-bpmn2-emfextmodel/src/main/resources/model

The drools.ecore and model.ecore were copied from this github repository and used as "inspiration"
for the jBPM5Extensions extension model. If the drools models change drastically over time, we
may have to manually merge changes into our extension model ecore. 