- dict_ becomes explicit on _get_state_attr_by_column, _set_state_attr_by_column...

- dict_ becomes explicit on _get_state_attr_by_column, _set_state_attr_by_column, others,
to reduce on expensive state.dict calls.
- internal getattr(), setattr(), getcommitted() methods
on ColumnProperty, CompositeProperty, RelationshipProperty
have been underscored, signature has changed.