Fixed #12642 - Add docs for has_[add|change|delete]_permission ModelAdmin...

                    kwargs["queryset"] = Car.objects.filter(owner=request.user)

                return super(MyModelAdmin, self).formfield_for_manytomany(db_field, request, **kwargs)

.. method:: ModelAdmin.has_add_permission(self, request)

    Should return ``True`` if adding an object is permitted, ``False``

    otherwise.

.. method:: ModelAdmin.has_change_permission(self, request, obj=None)

    Should return ``True`` if editing obj is permitted, ``False`` otherwise.

    If obj is ``None``, should return ``True`` or ``False`` to indicate whether

    editing of objects of this type is permitted in general (e.g., ``False``

    will be interpreted as meaning that the current user is not permitted to

    edit any object of this type).

.. method:: ModelAdmin.has_delete_permission(self, request, obj=None)

    Should return ``True`` if deleting obj is permitted, ``False`` otherwise.

    If obj is ``None``, should return ``True`` or ``False`` to indicate whether

    deleting objects of this type is permitted in general (e.g., ``False`` will

    be interpreted as meaning that the current user is not permitted to delete

    any object of this type).

.. method:: ModelAdmin.queryset(self, request)

    The ``queryset`` method on a ``ModelAdmin`` returns a