[1.2.X] Expanded InlineModelAdmin documentation a bit. Partial backport of [14882].

        .. versionadded:: 1.2

        ``fields`` can contain values defined in

        :attr:`ModelAdmin.readonly_fields` to be displayed as read-only.

        :attr:`~ModelAdmin.readonly_fields` to be displayed as read-only.

    * ``classes``

        A list containing extra CSS classes to apply to the fieldset.

.. attribute:: ModelAdmin.ordering

Set ``ordering`` to specify how objects on the admin change list page should be

ordered. This should be a list or tuple in the same format as a model's

``ordering`` parameter.

Set ``ordering`` to specify how lists of objects should be ordered in the

Django admin views. This should be a list or tuple in the same format as a

model's ``ordering`` parameter.

If this isn't provided, the Django admin will use the model's default ordering.

``InlineModelAdmin`` options

-----------------------------

The ``InlineModelAdmin`` class is a subclass of ``ModelAdmin`` so it inherits

all the same functionality as well as some of its own:

``InlineModelAdmin`` shares many of the same features as ``ModelAdmin``, and

adds some of its own (the shared features are actually defined in the

``BaseModelAdmin`` superclass). The shared features are:

- :attr:`~InlineModelAdmin.form`

- :attr:`~ModelAdmin.fieldsets`

- :attr:`~ModelAdmin.fields`

- :attr:`~ModelAdmin.exclude`

- :attr:`~ModelAdmin.filter_horizontal`

- :attr:`~ModelAdmin.filter_vertical`

- :attr:`~ModelAdmin.prepopulated_fields`

- :attr:`~ModelAdmin.radio_fields`

- :attr:`~InlineModelAdmin.raw_id_fields`

.. versionadded:: 1.1

- :meth:`~ModelAdmin.formfield_for_foreignkey`

- :meth:`~ModelAdmin.formfield_for_manytomany`

.. versionadded:: 1.2

- :attr:`~ModelAdmin.readonly_fields`

- :attr:`~ModelAdmin.formfield_overrides`

The ``InlineModelAdmin`` class adds:

.. attribute:: InlineModelAdmin.model

.. attribute:: InlineModelAdmin.extra

    This controls the number of extra forms the formset will display in addition

    to the initial forms. See the

    :doc:`formsets documentation </topics/forms/formsets>` for more information.