[1.2.X] Fixed #14840 -- Added crossrefs to related objects reference docs....

    A "related manager" is a manager used in a one-to-many or many-to-many

    related context. This happens in two cases:

        * The "other side" of a ``ForeignKey`` relation. That is::

        * The "other side" of a :class:`~django.db.models.ForeignKey` relation.

          That is::

                class Reporter(models.Model):

                    ...

          In the above example, the methods below will be available on

          the manager ``reporter.article_set``.

        * Both sides of a ``ManyToManyField`` relation::

        * Both sides of a :class:`~django.db.models.ManyToManyField` relation::

                class Topping(models.Model):

                    ...

            >>> b.entry_set.remove(e) # Disassociates Entry e from Blog b.

        In order to prevent database inconsistency, this method only exists on

        ``ForeignKey`` objects where ``null=True``. If the related field can't

        be set to ``None`` (``NULL``), then an object can't be removed from a

        relation without being added to another. In the above example, removing

        ``e`` from ``b.entry_set()`` is equivalent to doing ``e.blog = None``,

        and because the ``blog`` ``ForeignKey`` doesn't have ``null=True``, this

        :class:`~django.db.models.ForeignKey` objects where ``null=True``. If

        the related field can't be set to ``None`` (``NULL``), then an object

        can't be removed from a relation without being added to another. In the

        above example, removing ``e`` from ``b.entry_set()`` is equivalent to

        doing ``e.blog = None``, and because the ``blog``

        :class:`~django.db.models.ForeignKey` doesn't have ``null=True``, this

        is invalid.

    .. method:: clear()

        them.

        Just like ``remove()``, ``clear()`` is only available on

        ``ForeignKey``\s where ``null=True``.

        :class:`~django.db.models.ForeignKey`\s where ``null=True``.