added OrderConfirmView after the shipping backend, 
it just redirects to the payment backend but can be easily extended to display an order confirmation page
removed unused example shop template
added an example payment backend so it's easier to follow the checkout process when debugging
added example OrderConfirmView
oops, wrong url name
fixed tests
updated CHANGELOG
added cart reference to orders so we can clean them up
updated CHANGELOG
added test for cleaning up orders
made the test actually test what it says
Merge branch 'cleanorders' into orderstatus

Conflicts:
	CHANGELOG.rst
refactored order status: 
- removed unused PAYMENT and added CONFIRMING
- assignment of statuses is now linear
- moved cart.empty out of the ThankYouView and to the api
- includes data migration
updated changelog
re-added PAYMENT status since it might still be used by some backends, we should deprecate it
missing space in comment
Merge pull request #190 from Rue89/comment-typo

missing space in error message
Fixes create_from_cart, when argument state is used in one of the CartModifier
Separation of Concern for method OrderManager.create_from_cart:
By overloading the new method OrderManager.create_order_object
a user can more easily add his customized Order class.
Added description to Changelog