Label print updates (#399)

* Allow download of printed label

* Add setting for controlling label printing

* Control display of label printing via setting

* Refactor label printing functionality

- Move to helpers.dart
- Will be used for other label types also

* Factor out request for label templates

* Add label printing support for part

* Support label printing for stock location

* update release notes

lib/settings/settings.dart

@@ -13,8 +13,8 @@ import "package:inventree/settings/login.dart";
 import "package:inventree/settings/part_settings.dart";
 
 
+// InvenTree settings view
 class InvenTreeSettingsWidget extends StatefulWidget {
-  // InvenTree settings view
 
   @override
   _InvenTreeSettingsState createState() => _InvenTreeSettingsState();