#249 Created as modified

* fills modified attribute on new entries with created value automatically
* adds default ordering by last modified on table overviews

api/utils/serializer/v1/intervention.py

@@ -76,6 +76,7 @@ class InterventionAPISerializerV1(AbstractModelAPISerializerV1,
         created = create_action
         obj.legal = legal
         obj.created = created
+        obj.modified = created
         obj.geometry = geometry
         obj.responsible = resp
         return obj