Simplify event triggering

- add generic receivers for database actions
- exclude django_q tables, otherwise we get an infinite loop!

Ref: https://stackoverflow.com/questions/17507784/consolidating-multiple-post-save-signals-with-one-receiver/32230933#32230933

InvenTree/part/models.py

@@ -280,8 +280,6 @@ def before_delete_part_category(sender, instance, using, **kwargs):
         child.parent = instance.parent
         child.save()
 
-    trigger_event('category.deleted')
-
 
 def rename_part_image(instance, filename):
     """ Function for renaming a part image file
@@ -2186,10 +2184,8 @@ def after_save_part(sender, instance: Part, created, **kwargs):
     """
 
     if created:
-        trigger_event('part.created', part_id=instance.pk)
+        pass
     else:
-        trigger_event('part.saved', part_id=instance.pk)
-
         # Check part stock only if we are *updating* the part (not creating it)
 
         # Run this check in the background