Replace StockItemAttachmentCreate form

- Also replace drag-and-drop
- Add 'hidden' option for form fields
- Adds renderer for StockItem model

InvenTree/stock/serializers.py

@@ -288,6 +288,8 @@ class StockItemAttachmentSerializer(InvenTreeModelSerializer):
 
     attachment = InvenTreeAttachmentSerializerField(required=True)
 
+    # TODO: Record the uploading user when creating or updating an attachment!
+
     class Meta:
         model = StockItemAttachment