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

It is installed separately in transifex.sh for travis, and not required for developing on Oscar.

- Remove outdated material relating to old versions of Django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

Since there is no demo or us site anymore we can simplify the structure
somewhat by moving the sandbox one directory up

As per [their blog post of the 27th April](https://blog.readthedocs.com/securing-subdomains/) ‘Securing subdomains’:

> Starting today, Read the Docs will start hosting projects from subdomains on the domain readthedocs.io, instead of on readthedocs.org. This change addresses some security concerns around site cookies while hosting user generated data on the same domain as our dashboard.

Test Plan: Manually visited all the links I’ve modified.

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.

The demo site was not kept up to date with the recent changes in Oscar
due to time contraints. It should be moved to a separate demo repository
in the future.

This might be resurrected in a separate repository in the future.

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.

Vagrant support was removed from release 1.0. This commit removes mentions of it from the docs.

Closes #1559.

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.

I much prefer just using npm these days.

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 :)