Fixes #1145

This change ensures that the order model's FKs all use
on_delete=SET_NULL.

Cherry-picked (and adjusted) from 3e82571

Fixes #1130

This reverts ac7e8ee

Plus ensure the copyright notice is correct for the modified phone
number work.

Now using Napoleon :)

This avoids a pesky autodoc import issue that the debug toolbar creates when it
patches the URL conf.  It was preventing the EventHandler class from
being loaded via autodoc.  This fix solves that issue.

- Include screenshots.
- Expand sections up to deprecation.

- Expand the ref/apps docs. (Still lots to do here.)
- Split up the index page links for clarity.

Added to release notes & settings reference.

This reverts commit 7075ba6594.

It's not used anywhere in Oscar's code. It also doesn't feel right, as
adding categories via breadcrumbs is an undocumented hackish solution
anyway.

Two apps were forgotten. Also extended notes to mention new partner
dashboard.

It's a nice app to handle non-blocking email sending.

In our instructions, it wasn't entirely clear that virtualenvwrapper is
required for setup.

Fixes #1088

nose-django-querycount gives individual and total query counts. This is
helpful to double-check changes that claim to affect query count
(e.g. #1056).
Total query count gives a quick overview, and diff'ing the output for
two different branches works well.

This is to enable some coarse metrics of who is using Oscar.  We just
look at the referer header to get a rough idea of which sites are using
Oscar.

This is an important measure for Tangent, Oscar's sponsor.  It's
documented in the release notes and we'll make sure everyone knows when
Oscar is released.  It's easy to opt out of.

Fixes #656

Fixes #1028

Fixes #1021

Images are resized on the template level with Sorl, so having
those properties only leads to confusion. They were not used by stock
Oscar. Furthermore, thumbnail_url returned the full-size image URL,
which is wrong.

Fixes #1011

Two links needed to be corrected.

Done as it became apparent in #968 that further clarification is needed.

This setting never did anything. Added documentation for it being
dropped.

Fixes #983

The customisation section required some changes as it's not often
necessary to override the root application instance to change URLs or
views of subapps.

Those documents lived in ref/, but really aren't reference documents.
Topics/ is a more appropriate place for them.

bootstrap-wysihtml5 was too buggy.  I was trying to avoid TinyMCE but it ended up
being the easier to use.  I tried with CKEditor but it proved too
difficult to configure.

Fixes #757
Fixes #946
Fixes #945
Fixes #944

Previous names were ambiguous as to whether discounts were being
included or excluded.