Fixed #14007 -- Added model discovery in models module without the need to specify app_label.

Thanks mark@ and Aramgutang for work on the patch.

tests/model_package/models/article.py

@@ -6,6 +6,3 @@ class Article(models.Model):
     sites = models.ManyToManyField(Site)
     headline = models.CharField(max_length=100)
     publications = models.ManyToManyField("model_package.Publication", null=True, blank=True,)
-
-    class Meta:
-        app_label = 'model_package'