Fix mising EDatatype ePackage registration

Each generated EDatatype instance was implicitly bound to a container
using internal references. This commit introduce a more "official" way
of registering them. This modification only impacts users that want to
do metamodel reflexive operations.

Author: aranega

pyecoregen/templates/package.py.tpl

@@ -53,7 +53,7 @@ otherClassifiers = [{{ element.eClassifiers | select('kind', ecore.EDataType) |
 
 for classif in otherClassifiers:
     eClassifiers[classif.name] = classif
-    classif._container = {{ element.name }}
+    classif.ePackage = eClass
 
 for classif in eClassifiers.values():
     eClass.eClassifiers.append(classif.eClass)