Used auto-numbered lists in documentation.

docs/howto/custom-model-fields.txt

@@ -699,12 +699,12 @@ complex conversions between your Python types and your database and
 serialization formats. Here are a couple of tips to make things go more
 smoothly:
 
-1. Look at the existing Django fields (in
+#. Look at the existing Django fields (in
    :file:`django/db/models/fields/__init__.py`) for inspiration. Try to find
    a field that's similar to what you want and extend it a little bit,
    instead of creating an entirely new field from scratch.
 
-2. Put a ``__str__()`` method on the class you're wrapping up as a field. There
+#. Put a ``__str__()`` method on the class you're wrapping up as a field. There
    are a lot of places where the default behavior of the field code is to call
    ``str()`` on the value. (In our examples in this document, ``value`` would
    be a ``Hand`` instance, not a ``HandField``). So if your ``__str__()``
@@ -736,12 +736,12 @@ A few suggestions
 In addition to the above details, there are a few guidelines which can greatly
 improve the efficiency and readability of the field's code.
 
-1. The source for Django's own ``ImageField`` (in
+#. The source for Django's own ``ImageField`` (in
    ``django/db/models/fields/files.py``) is a great example of how to
    subclass ``FileField`` to support a particular type of file, as it
    incorporates all of the techniques described above.
 
-2. Cache file attributes wherever possible. Since files may be stored in
+#. Cache file attributes wherever possible. Since files may be stored in
    remote storage systems, retrieving them may cost extra time, or even
    money, that isn't always necessary. Once a file is retrieved to obtain
    some data about its content, cache as much of that data as possible to