[Port] Adjust extraction of profile fields for display

Old version was picking up pointer fields and failing to handle
DoesNotExist exceptions.

(cherry picked from commit c89480973817c8a503a2ccfbf147ee68eb808c37)

Conflicts:
	oscar/apps/customer/views.py
[Port] Handle case where anon order status view is not registered

Some sites may not include that URL and so we should swallow the
resolution exception to enable checkout to process as normal.

(cherry picked from commit 70ddc185b1aae3573ce135f57e8048b007dca95a)

Conflicts:
	oscar/apps/checkout/mixins.py
Improve testrunner

- Use long version of options
- Moar comments!
- Allow verbosity to be specified
Use {% static %} for images

This allows more flexibility with where images are stored, e.g. when
using django-storages.

Thanks to @sparky300 for reporting. Fixes #825
Docs on customising Oscar's communications

Credit and thanks go to @seddonym (David Seddon).
Docs: Add product class and category to glossary
Delete unused fields on [Shipping|Payment]EventType

is_required and sequence_number are removed. That also makes the unused
get_prerequisites function obsolete.

Those fields were added with the idea that those event flows are linear,
but all implementations assume a non-linear pattern.
Ensure Oscar always displays timezone-aware datetimes

In a few cases, django.templatefilters.date was used to format a
datetime as string. This filters expects localtime, but was always
passed time in UTC.
Introduced a helper function that should be used instead of the template
filter.
Add two settings related to custom user model
Fix direct import of auth user model
Make migrations work with custom user model
Deprecate get_product_base_queryset in favor of manager method

This eases customisation and is the right place for it anyway.
Don't require attributes for product variants

Previously, a variant was only added to the "Pick a variant" dropdown
when it had one or more product attributes set. This helps distinguish
variants with the same title, but should not be required by Oscar as
one can also set different titles for the variants.
Consistently list mixins before base classes

Most mixins will override functions of base classes and hence belong
before them.

Fixes #818
Merge remote-tracking branch 'upstream/master'