Update release notes with several recent changes, and refactor wording of some existing notes.
Update release notes with several recent changes, and refactor wording of some existing notes.

sasha0/django-oscar,solarissmoke/django-oscar,solarissmoke/django-oscar,django-oscar/django-oscar,solarissmoke/django-oscar,solarissmoke/django-oscar,django-oscar/django-oscar,sasha0/django-oscar,django-oscar/django-oscar,django-oscar/django-oscar,sasha0/django-oscar,sasha0/django-oscar