Made cosmetic cleanups to docs/ref/contrib/contenttypes.txt

* :attr:`~django.contrib.contenttypes.models.ContentType.model`

  will be set to ``'site'``.

.. _the verbose_name attribute: ../model-api/#verbose_name

Methods on ``ContentType`` instances

====================================

:class:`~django.contrib.auth.models.User` model::

    >>> from django.contrib.contenttypes.models import ContentType

    >>> user_type = ContentType.objects.get(app_label="auth", model="user")

    >>> user_type

    >>> ContentType.objects.get(app_label="auth", model="user")

    <ContentType: user>

And then use it to query for a particular

lookup::

    >>> from django.contrib.auth.models import User

    >>> user_type = ContentType.objects.get_for_model(User)

    >>> user_type

    >>> ContentType.objects.get_for_model(User)

    <ContentType: user>

.. module:: django.contrib.contenttypes.fields

If you know which models you'll be using most often, you can also add

a "reverse" generic relationship to enable an additional API. For example::

    from django.db import models

    from django.contrib.contenttypes.fields import GenericRelation

    class Bookmark(models.Model):

        url = models.URLField()

        tags = GenericRelation(TaggedItem)

into account. For now, if you need aggregates on generic relations, you'll

need to calculate them without using the aggregation API.

.. module:: django.contrib.contenttypes.forms

Generic relation in forms