Created|Deleted refactoring

* refactors base attributes created and deleted into UserActionLogEntry foreign keys
* refactors all related queries and process logic
* fixes binding_on into binding_date in intervention/detail/view.html
* adds basic __str__ for some models
*

konova/admin.py

@@ -13,8 +13,7 @@ from konova.models import Geometry, Document, Deadline
 class GeometryAdmin(admin.ModelAdmin):
     list_display = [
         "id",
-        "created_on",
-        "created_by",
+        "created",
     ]
 
 
@@ -23,8 +22,7 @@ class DocumentAdmin(admin.ModelAdmin):
         "id",
         "title",
         "comment",
-        "created_on",
-        "created_by",
+        "created",
     ]