[3.2.x] Refs #4027 -- Added Model._state.adding to docs about copying model instances.
[3.2.x] Refs #4027 -- Added Model._state.adding to docs about copying model instances.

Backport of 0fd05df7b5690fb1b675e1b4d9c92bb22ff74360 from master

koordinates/django,koordinates/django,koordinates/django,wkschwartz/django,wkschwartz/django,wkschwartz/django,wkschwartz/django,koordinates/django