This completes the move away from partner wrappers to strategies. All
the methods for determining price and availability information have now
been removed from the partner classes.

The helper policy class ("DelegateToStockRecord") have been removed too
as they no longer have methods to call on the stockrecord.

Using "partner" is easily confused with passing an actual partner
instance.

This should always be used instead of Django's silent version.

Tests should now pass.

Introduced get_primary_address and get_address_for_stockrecord. I opted
to implement rudimentary logic supporting only one PartnerAddress
instead of raising NotImplemented. I'm assuming that given the demand
for multiple partners scenario, it is more likely than not that a user
will need to store an address for a partner.

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.

Fixes #376

* Fixes bug with prefetch_related where looking up secondary relations
  raises a DoesNotExist exception.
* Reworks cached partner map to use PKs instead of names.
  Availability logic from product class is looked up in product obj
  rather than in wrapper to avoid unnecessary queries.

Turns out this is a bit confusing.  Better for it to do nothing by
default and this behaviour can be enabled when it is needed.

Also split them into unit and functional tests.

These are a simple model that books into the post_save of a stockrecord.

* Converted to abstract models
* Added tests for conditions

This seems to be a simpler and better place for the price calculation at
the moment.  We could introduce a calculator object at some point to
separate the responsibilities.

Made product models abstract in the standard way.

Completed the models for the order package too.  Added admin files