The ability to include(admin.site.urls) was removed in Django 2.

- Remove outdated material relating to old versions of Django
- State that Oscar assumes that the email field is unique
- Update a number of links to Django documentation.
- Minor fixes to other bits of documentation.

Load i18n context processor from django.template instead of django.core as fix for Django 1.10

Conflicts:
	docs/source/internals/getting_started.rst

Cherry-picked from #1934, because that PR was onto releases/1.1 and I
merged it to there by accident.

django-compressor used to trigger processing of the less files during
development. But with the browser-based compiler, an easy replacement is
available. This even lowers the barrier to altering styles, because
getting npm up and running isn't required.

Offline compilation isn't impacted.

Using the most current less version seems to not cause any trouble, so I
removed the version requirement.

The TEMPLATE_DIRS and TEMPLATE_CONTEXT_PROCESSORS are no longer separate
settings thus given an example for the new TEMPLATES setting.

Also note that the user should include widget_tweaks in the
INSTALLED_APPS setting.

Closes #1571.

This reflects the change in the repo URL.

It's necessary to add South before running migrate to successfully
create the database.

Cherry-picked by @maikhoepfel from #1545.

Had to rename to new method name and re-add a link.

This commit updates the Getting started guide and highlights the upgrade
path for Oscar 0.8.

The Django admin often enough does not work or not as expected; that
isn't communicated clearly enough. This commit hopefully clarifies
things a bit.

I started looking at this because on the mailing list, having the UK as
only shipping country led to confusion. This is mostly due to the
shipping address form hiding the country field if there's only one
country enabled, but all the validation then requiring UK postcodes and
phone numbers.

It's bothered me for a while that we're using a fixture to populate the
countries, which is at risk of becoming stale.
pycountry offers an excellent data source for a list of countries, so I
polished an existing management command to use it to populate the
country database.

This commit has two immediate effects:
* New setups will use a more current country database
* By default, all countries will be marked as shipping countries

pycountry also ships with localised names of the countries, which should
allow us to populate the database with localised country names.

Two people on the mailing list tripped over the location helper, so it's
now included right next to where it is used.

The helper is now also used in a few more spots in the settings.

The non-camelcased class has bothered me for a long time.
We can remove the deprecated spelling for version 1.0 :)

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

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 struggled, so I thought I'd document it.

A few little bits caught my eye. Moved the django-compressor tip nearer
to the section about INSTALLED_APPS.

This makes the docs navigation a lot more useful, and it gives it a bit
more coherent structure.

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

Just crossing items off my bucket list.

Sitemaps isn't enabled by default anymore, which is now mentioned.

Mentioned on the mailing list
https://groups.google.com/d/msgid/django-oscar/720d5205-53b0-4ad0-b62e-8eba70af891e%40googlegroups.com

Turns out Django>=1.4 does include staticfiles and messages in its
default INSTALLED_APPS.

Fixes #814

Source: https://groups.google.com/forum/#!msg/django-oscar/AbjNVCPnwIM/cWieN8AkwSIJ

Spotted here: https://groups.google.com/forum/#!msg/django-oscar/539hyvFPNso/6pXa-M3cfhEJ

includes django.core.context_processors.tz.