This order offers the simplest API for common needs - as evidenced by the
fact that the apply_offers crook could be removed from two test files,
saving on imports as well.

This (possible backwards incompatible) change means subclassing and
customising shipping methods becomes much easier. Now that shipping
methods are stateless, we can instantiate at compile time and assign
them to the repository instance.

This commit also renames internal methods of the shipping repository
in as the 'prime' notion is no longer valid (as we're not injecting a
basket into each method).

We now need to pass in the shipping charge explicitly as well as the
method. The way that the shipping discounts are persisted is also
adjusted.

To support multi-currency sites.  This commit also made the order totals
a mandatory input for creating an order, which meant quite a few tests
had to change to support the new API.

Should have checked this before pushing before...

Use charge_incl_tax instead of basket_charge_incl_tax().  This is
clearer.

Backwards compatible versions of the old methods are kept for now.

Related to #805

Hmmm, this turned out to be a monster commit.  This change allows the
basket to be able to correctly calculate prices including tax.

It also requires a whole load of test changes since all baskets now
require a strategy instance to be assigned.

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.

They aren't treated specially any more.  They become part of the
'applications' collection rather than being attached to the basket.