[IMP] models: "X in self" is now equivalent to any(X == rec for rec in self)

Fix modules with code like "record.id in other.stuff_ids".
[IMP] models: inherited fields are related fields read as the current user

Add an attribute 'related_sudo' (True by default) for related fields.
A related field is computed as superuser if related_sudo is True.

Add explicit related fields 'name' and 'email' on 'res.users', as these should
be readable by the public user with module website_forum.