* Silently skip stock allocation manipulations if the product class doesn't track stock.

* Make it possible to cancel/consume stock allocations without line args.

You can now do:
consume_stock_allocations(order)
cancel_stock_allocations(order)
without the lines / line_quantities arguments.

Better to use filenames which are commonly used in the python word then
custom ones.

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.

As they save stuff...

Fixes #376