Toggle full name display of users (#5927)

* Add option to display full names instead of usernames

* InvenTree Setting added to allow for admins to choose full names
  over usernames for display in the web GUI

* Fix FA icon for settings page

* Remove debug print

InvenTree/common/models.py

@@ -1874,6 +1874,12 @@ class InvenTreeSetting(BaseInvenTreeSetting):
             ]
         },
 
+        'DISPLAY_FULL_NAMES': {
+            'name': _('Display Users full names'),
+            'description': _('Display Users full names instead of usernames'),
+            'default': False,
+            'validator': bool
+        }
     }
 
     typ = 'inventree'