- Move Oscar app configs into Django app config classes
- Rename Oscar/Django apps' app config module
- Remove "oscar.get_core_apps()" and its app overriding
- Remove "oscar.OSCAR_CORE_APPS"
- Port app forking code to work with Django app registry
- Port class loading code to use app configs to get app properties

Previously, validation did not pass when current locale is "en-gb" and URL is "/de/catalogue/" and visa versa due to default Django URL resolvers behaviour  - they do not take into account all locales, only current.

Now after ConditionalOffer deleted will be deleted related Benefits and Conditions models (through post_delete signal) if they are no longer used by other offers (with exception of custom benefits/conditions). Plus some small changes related to PEP8 and typos.

The copying of the email address within the datamigration isn't really
optimal when a site has a large number of users and send emails.

Most real-world instances will use postgresql instead of sqlite so it's
better to use postgres for the tests. This also allows us to easily add
tests for concurrency issues which is not supported by sqlite

This fixes a DeprecationWarning

This also updates the pytest dependencies

 - Set Meta.app_label on models created in the tests
 - Use logging.NullHandler instead of django.utils.log.NullHandler
 - Use oscar.core.loading.get_model() instead of django's get_model
 - Remove template tags '{% load url from future %}'

This has been around since forever, and removing it is overdue. I took
the opportunity to slightly improve the urls.py files.

The changes should be obvious and non-controversial. Under Django 1.7+,
the AppConfig is used to register signal receivers instead of just
registering then when models are registered.

Adds new functional tests for ShippingAddressView, PaymentDetailsView
and ThankYouView.
It's the second part of #1645.

Notes

* Adds a custom template to be able to test some functionalities of
  PaymentDetailsView
* Adds an helper to the CheckoutMixin

The config was picking the wrong directory so the custom test templates
were not used during tests.

Notes

- Fix missing i18n load tags
- Remove mixed tab/space indentation
- Add two settings tests

When adding a migration on master, I discovered that the new-style
migrations were strongly out of sync; Django wanted to create new
migrations for almost every app. That was surprising given that no model
changes were made since building that set of migrations.

The issue is that they were built with Django 1.7 RC2, and we've since
switchted to RC3. If I'd have to guess, I'd say the following issue is
responsible for it:
2da20379c0

As beta 1 is only a day old and it doesn't cause major headaches, it was
decided that it's easiest to release a new set of migrations. And pray
to the gods of Python that we won't have a similar situation again
before the Django migrations framework stabilises.

We only needed it because Django 1.4 shipped with a pretty old version
of six. Support for that has been removed, and Django 1.5 ships with six
1.6.1, which is more current than we required.

This nicely avoids an issue with django-extra-views pinning a six
version which caused the sandbox build to fail:
https://travis-ci.org/tangentlabs/django-oscar/jobs/32223978#L971

Native migrations created with Python 2 differ from ones created with
Python 3. More importantly, they failed when used in Python 3, but not
vice versa. This is caused by field names being marked as byte strings
when using Python 2.

This rewrites the native migrations, which probably isn't a bad thing
either, because they were created with a pre-RC2 version of Django, and
Django 1.7 has since seen a few more migration-related fixes.

It's likely Django now does the correct thing and generates Python 2 and
3 compatible migrations under both versions of Python.

To create test databases, the Django test runner calls the 'migrate'
management command, and I think the current Nose test runner calls
'syncdb', which under Django 1.7 is aliased to 'migrate'.

This command inspects the migration graph to figure out the migrations
to run. So it inspects the migrations that ship with Oscar. Some of them
depend on the partner or customer migrations. The test suite swaps out
those apps. Until now, the command then couldn't find the initial
migrations and would fail with a dependency error.

As far as I can tell, there's no good way to just call what used to be
"syncdb" and ignore migrations completely. So for now, we will have to
create migrations for the test apps that replace Oscar.

The app label needs to be the same that is used in the AUTH_USER_MODEL
setting to specify the custom user. For Oscar's AbstractUser, we
shouldn't set an app label; Django's autodetection should work in most
cases.

It in facts works for the test suite's custom user as well; but as we
specify app labels everywhere, we might as well specify it there.

Also register the signal receivers in the ready() method for 1.7+

The function essentially does two things:
1. it applies a prefix - the first argument - to the given urls. In no
   instance a prefix was given
2. it calls url() for simple tuple or list elements in the given iterable.
   Cases where such a tuple or list was passed to patterns have been
   replaced by direct calls to url()

2 allowed for both calls to url() and simple tuples to be listed in
get_urls() and similar places. This allowed for unnecessary variation.
Always calling url() makes the url lists look less noisy and more uniform,
allowing the reader to focus on the actual differences of the urls instead
of superfluities.

django.conf.urls.patterns will also undergo deprecation starting from
Django 1.8. This commit anticipates that change.

https://docs.djangoproject.com/en/dev/releases/1.8/#django-conf-urls-patterns

I messed up when moving Alex Moon's code to oscar.core.compat and used
the wrong User model, defeating the point of the exercise.

This is fixed now, and the filter is also used for the UserForm that
gets used in the account section.

Fixes #1283.
Fixes #1282.

(cherry picked from commit 20df512eda)

Conflicts:
	oscar/apps/customer/forms.py

I messed up when moving Alex Moon's code to oscar.core.compat and used
the wrong User model, defeating the point of the exercise.

This is fixed now, and the filter is also used for the UserForm that
gets used in the account section.

Fixes #1283.
Fixes #1282.

This required:
* Moving Django's i18n urls into the main urls.py and outside of the
  scope of Oscar's main application class, because they need to live
  outside of the scope of i18n_patterns
* Add a language-code stripped version of the current URL to the
  template context to get the language switcher working.

I also updated the language switcher code to mimic what is currently
given as an example in Django's docs.

Fixes #797

Tests for separator and uppercase options.

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

Taken from django-extensions with some adapting to our needs.

Django 1.4 is not supported anymore, hence we can remove it.

Previously, the test suite ran with a custom user model for Django >=
1.5, but it didn't subclass Oscar's AbstractUser.  This commit adjusts
the custom user model to subclass Oscar's so we can test functionality
within the custom user class.

This does require a change to the way tests authenticate as we don't
actually use the username field.

This reverts fa1f8403 which moved them from models.py to __init__.py.
As reported by @mvantellingen, importing receivers from __init__.py
breaks the way models are normally overridden as it causes the core
models.py to get imported before the custom one.

We need to move back to the old system and will need to advise that the
debug toolbar needs to be set-up explicitly to avoid circular import
issues with models.

Fixes #1159
Original issue #1125