=> __init__ + __getattribute__ now handle only the Django inheritance
references that are needed ('modela_ptr', 'modelc' etc.), avoiding
unnecessary conflicts with field names.
instead of app-label and model-name (suggested by Ilya Semenov in issue 3).
This is a cleaner and more efficient solution, and applabel/modelname
are not stored redundantly in additional tables any more (the polymorphic models).
This should be the final DB schema now (sorry for any inconvenience).
Also some minor documentation updates.