Changes to stock validation are stricter now.

It's not really needed as it doesn't make sense to simply add an address
to your addressbook as part of checkout.

This allows updating code in both places, if necessary. Getting Django
1.5 support would be painful otherwise. This also removes the circular
dependency of django-oscar-testsupport on Oscar.

The requirements were merged. The imports were updated
accordingly. Unused imports in the touched files were removed. No
further changes.

Change to required address fields was causing the shipping address step
to fail.

OSCAR_REQUIRED_ADDRESS_FIELDS allows setting which fields are required.
The use case is that post codes are expected to be required, but many
countries don't actually use them.

Required several schema changes:
* Add num_applications to offer model to track number of times an offer
  has been applied within an order.
* Add max_global_applications to offer model to set a limit on how many times an offer
  can be used.
* Add frequency to order discount to provide insight into how many times
  an offer was applied for a particular order.

Structure of dashboard changes to talk about offer 'availability'
instead of assuming a start- and end-date.

Fixes #376

It didn't exist when I wrote patch_settings but now there's not point
having two versions of the same thing.

This view has a form that assumes anon checkout is allowed, which it
isn't always.  Treating it as a special case was causing it to be
displayed when it shouldn't.

Also added tests for vouchers

Also split them into unit and functional tests.

This allows the preview to accept two types of POST:

1) POSTing from payment-details to submit sensitive data, which gets
   re-rendered in the preview template
2) POSTing from preview to submit the orderk

New look is a bare form for each stage as opposed to showing all the
information.

* The views check that the guest email address has been entered.
* The email address is written out against the order.
* An email confirmation is sent to the guest user email address.

This uses a few new methods in oscar.core.application.Application which
enable custom decorators to be set for given view fns.

The main use case at the moment is to make it easy to ensure that
checkout is not available to non-logged-in users when
OSCAR_ALLOW_ANON_CHECKOUT is set to False.

tests