Slight fixes to related fields reference to avoid conflicting target names

.. currentmodule:: django.db.models.fields.related

This document describes extra methods available on managers when used in a one-to-many or many-to-many related context. This happens in two cases:

.. class:: RelatedManager

    A "related manager" is a on managers 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::

          In this example, the methods below will be available both on

          ``topping.pizza_set`` and on ``pizza.toppings``.

    These related managers have some extra methods:

    .. method:: add(obj1, [obj2, ...])

        Adds the specified model objects to the related object set.

            .... )

            >>> e.save(force_insert=True)

    Note that there's no need to specify the keyword argument of the model that

    defines the relationship. In the above example, we don't pass the parameter

    ``blog`` to ``create()``. Django figures out that the new ``Entry`` object's

    ``blog`` field should be set to ``b``.

        Note that there's no need to specify the keyword argument of the model

        that defines the relationship. In the above example, we don't pass the

        parameter ``blog`` to ``create()``. Django figures out that the new

        ``Entry`` object's ``blog`` field should be set to ``b``.

    .. method:: remove(obj1, [obj2, ...])

            >>> 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 is invalid.

        ``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

        is invalid.

    .. method:: clear()

            >>> b = Blog.objects.get(id=1)

            >>> b.entry_set.clear()

    Note this doesn't delete the related objects -- it just disassociates them.

        Note this doesn't delete the related objects -- it just disassociates

        them.

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

    where ``null=True``.

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

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