Oscar by default deleted image files and thumbnails. That is usually
fine, but has been an issue when using remote storages like S3. This
change also makes the only remaining import from sorl optional, hence
paving the way to making it completely optional.

Fixes #1373.

The howto recipe on shipping has been rewritten to describe the new
changes to shipping functionality. The old shipping app reference has
been merged in too to avoid duplication.

Importing things in settings is discouraged. But until now,
OSCAR_SLUG_FUNCTION could only be set as a callable, which requires
importing. It's now been updated to use the import_string function.

Seems like a good practice to define them explicitly.

Cherry-picked from d755aae.

The getting started guide now explicitly mentions copying the "missing
image" image when working with a remote file storage. Was raised in
issue #1314.

Oscar is slowly adding better support for switching languages on the
fly. That also means that locales need to be switched.

The issue this commit tries to fix is that when switching languages, the
locale for rendering prices doesn't change, and hence prices are
formatted incorrectly.
Oscar used to require hardcoding the locale for prices via
OSCAR_CURRENCY_LOCALE. I'm not sure what the reasoning behind this was,
because as far as I'm aware, the locale can be auto-detected from the
current language. This not only reduces complexity, but nicely works
when switching languages.

This allows importing a class or attribute by the reasonably common
string notation, which is useful for e.g. settings. When using settings,
we should prefer absolute imports over using get_class, because that
limits us to modules in INSTALLED_APPS.

We send the user's email address too.

* It can now be specified in OSCAR_DASHBOARD_DEFAULT_ACCESS_FUNCTION
* nav.py and menu.py were split up so that Node can be dynamically
  loaded and hence overridden

I recently needed to alter the access function and realised it's not as
easy as I thought.

Allow using a different app than promotions as the homepage view.

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

Now using Napoleon :)

- 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.

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

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

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

 - 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.

Add documentation and hide visibility from UI

We currently mention it in internals/sandbox.rst. I've added a note to
the dashboard app (ref/apps/dashboard.rst), the sandbox/urls.py and
expanded on the feature explanation on index.rst.

Fixes #816

They were missing the autodoc documentation for views (abstract) and
abstract models.
Also added two docstrings to the views in the promotions app to have
them showing in the autodoc.

Also adds a docstring to the is_discountable AbstractProduct

* Use correct directives in signals.rst
* Removed newline in glossary.rst that broke sorting of glossary terms
* Removed syntax warning for upgrading.rst

Some of them are rather basic, but it's a start.

Fixes #697

* Better wordings for the individual steps
* Mentioned necessary copying of migrations directory
* Fixed wrong prerequisites in examples
* Glossary typo fixed

Commonly used terms should be explained there.

- Added stubs for both apps
- Switched to using :automodule: for abstract models instead of
  individual :autoclass:
- Added instructions on creating a Partner and ProductClass instance
  when setting up a new Oscar instance

Plus some general reorganisation.