Override dashboard apps - duplicate label

[Pablo Camino Bueno]

Hello,

I'm customizing several dashboard apps. Most of them work as expected, but there are 2 of them that throw an error when added in settings.py. 

If I include 'dashboard.reviews' in get_core_apps, this happens:

File "...\lib\site-packages\django\__init__.py", line 27, in setup

    apps.populate(settings.INSTALLED_APPS)

  File "...\lib\site-packages\django\apps\registry.py", line 89, in populate

    "duplicates: %s" % app_config.label)

django.core.exceptions.ImproperlyConfigured: Application labels aren't unique, duplicates: reviews

Same thing happens with 'dashboard.shipping'.

[Pablo Camino Bueno]

It seems they need to set default_app_config in __init__.py