Order extra lines (#632)

* Define classes for extra line item

* Display PO extra line items

- Also, some refactoring

* Support extra line items for sales order

* linting fixes

* Update release notes

lib/widget/stock/stock_list.dart

@@ -5,7 +5,6 @@ import "package:inventree/inventree/stock.dart";
 import "package:inventree/widget/paginator.dart";
 import "package:inventree/widget/refreshable_state.dart";
 import "package:inventree/l10.dart";
-import "package:inventree/widget/stock/stock_detail.dart";
 import "package:inventree/api.dart";
 
 
@@ -146,7 +145,7 @@ class _PaginatedStockItemListState extends PaginatedSearchState<PaginatedStockIt
         )
       ),
       onTap: () {
-        Navigator.push(context, MaterialPageRoute(builder: (context) => StockDetailWidget(item)));
+        item.goToDetailPage(context);
       },
     );
   }