The old Repository class wasn't thread safe as the method instances were
created at compile time.  Since the instance is configured by setting
the basket for each request, this poses thread safety issues as two
requests could share the same method instance (one of which would have
the wrong basket assigned).

This change fiddles with how the methods are handled, ensuring that they
are instanciated within the instance methods so that thread-safety
issues go away.

Shipping methods need a gentle rewrite for v0.7 to ensure they aren't
vulnerable to such issues.

 - make sure all pages are linked from somewhere
 - prohibit double indexing of source code modules
 - remove old unused offers (we use GIT, no need to keep old files)
 - use local version of Oscar logo

Fixes #921

With details of new prices/availability structure.

is_required and sequence_number are removed. That also makes the unused
get_prerequisites function obsolete.

Those fields were added with the idea that those event flows are linear,
but all implementations assume a non-linear pattern.

Some method defaults have been removed to make it more explicit when
things are loaded.

Faster is better!

Only search_default needed correcting.

- Add new block for payment tab
- Rename transactions block
- Provide transactions in get_context_data
- Better handling of empty iterables

is_highlighted is now an integer and works similar to the common
"ordering" fields. The higher the number, the higher the country will be
moved up in the list.

Fixes #720, #725

Filenames can easily get longer than 100 characters, and that causes
Django to fail hard (I think with a DatabaseError), because it's
currently not validated (see Django #11027)

This fix increases the character limit to 255 chars. Going much higer
can cause trouble with MySQL.

Fixes #625. Thanks for reporting go to @soloweb.

To be consistent with the rest of Oscar.

This makes more sense than keeping it as a method.

Hattip to @BuddhaOhneHals for doing this in the first place.
Unfortunately, I couldn't (be bothered to) merge the original commit as
the merge conflicts were too painful to resolve - simpler to just
reapply the same change myself.

Fixes #466

Update release notes too.

The parameters have been changed to use request, not request.basket.