#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/ema.py

@@ -85,6 +85,7 @@ class EmaAPISerializerV1(AbstractModelAPISerializerV1, AbstractCompensationAPISe
         )
         created = create_action
         obj.created = created
+        obj.modified = created
         obj.geometry = geometry
         return obj