Add ModelWithFieldAttributes *before* PolyModel, so that everything does not
become a "ModelWithFieldAttributes" in the Datastore.
The way PolyModel works, each Model class hierarchy is stored in the Datastore
as the class that directly inherited from PolyModel. So, we do not want to
insert ModelWithFieldAttributes *after* PolyModel by inheriting *from*
PolyModel, or everything would just be a ModelWithFieldAttributes in the
Datastore, instead of Person, Work, Group, etc.
This is an optional add-on app, flatpages.
For full documentation, see either of these:
* The file docs/flatpages.txt in the Django distribution
* http://www.djangoproject.com/documentation/flatpages/ on the Web
Both have identical content.