Build line labels (#5034)

* Adds BuildLineLabel model

- New type of label for printing against BuildLine objects

* Add serializer for new model

* Add API endpoints for new label type

* Add hooks to BuildLine table

* Create default label

- Create an example BuildLineLabel object

* Add admin integration

* Fix js code

* Use two-tiered template

- Allows base template to be updated

* Improve default label

* Add docs pages for labels

* Update nav

* Documentation for new label

* Add permission role

* Bump API version

InvenTree/users/models.py

@@ -136,6 +136,7 @@ class RuleSet(models.Model):
             'stock_stockitem',
             'stock_stocklocation',
             'report_buildreport',
+            'label_buildlinelabel',
         ],
         'purchase_order': [
             'company_company',