#50 Overlaying geometries

* refactors geometry field into GeoReferencedMixin, holding more handy methods and used in all models, formerly holding the geometry field
* refactors backend admin configuration, so modified, deleted and created are not editable in the backend which also skips loading of all possible choices
* fixes typo in sanitize_db command
* introduces GeometryConflict model, holding a link between two geometries, where one overlaps the other
* adds first (WIP) messages into detail views of ema and intervention for test purposes

intervention/views.py

@@ -255,8 +255,7 @@ def detail_view(request: HttpRequest, id: str):
         "LANIS_LINK": intervention.get_LANIS_link()
     }
 
-    if not is_data_shared:
-        messages.info(request, DATA_UNSHARED_EXPLANATION)
+    request = intervention.set_status_messages(request)
 
     context = BaseContext(request, context).context
     return render(request, template, context)