Added documentation about the "app.Model" relation syntax introduced by [7185]

    class Manufacturer(models.Model):

        # ...

Note, however, that you can only use strings to refer to models in the same

models.py file -- you cannot use a string to reference a model in a different

application, or to reference a model that has been imported from elsewhere.

Note, however, that this only refers to models in the same models.py file -- you

cannot use a string to reference a model defined in another application or

imported from elsewhere.

**New in Django development version:** to refer to models defined in another

application, you must instead explicitially specify the application label. That

is, if the ``Manufacturer`` model above is defined in another application called

``production``, you'd need to use::

    class Car(models.Model):

        manufacturer = models.ForeignKey('production.Manufacturer')

Behind the scenes, Django appends ``"_id"`` to the field name to create its

database column name. In the above example, the database table for the ``Car``