[WIP] - Refactor ORM with VirtualField and CompositeField

[auvipy]

This is a very early WIP draft. I am still working on figuring out some issues and proper approaches.

I will share it on mailing list soon after I think it's ready for initial review. Any improvement suggestions are highly welcome.

[ShaheedHaque]

I wonder if it is worth taking into account what something like django-polymorphic needs? (I'm not myself qualified to say what that might be).

[auvipy]

i think django-polymorphic should be improved by the changes if done correctly