This change adds a uniqueness constraint on user addresses to prevent
duplicates.  A few changes follow:

- The user address forms in account and checkout are modified to take a
  user as a constructor arg so uniqueness can be checked.

- The assignment of a user when creating a new address has been moved
  into the form.

Previous version was not filtering by user.

It's possible that a user could select an address to ship to but then
delete it before checkout is complete.  This change raises an
UnableToPlaceOrder exception in such circumstances.

Also I moved the generate_hash fn up to the Address superclass as it's
possible that it might be used in other Address classes.

OrderPaymentMixin has a new method `get_shipping_address` which returns
shipping address without saving it. Useful as part of checkout process.

It makes it easy to mark a method deprecated and is easy to look up
deprecated methods via grep (look for '@deprecated').

Email address is more appropriate to display than Guest.

Fixes #740

Caused by reworking of the user creation form.

The message context includes the variable include_buttons, but the
template checks for presence of show_buttons. This led to the buttons
never being displayed.

- Expand width of address block
- Wrap edit user address form in "well"
- Add extra blocks to preview template, splitting out shipping address,
  contact number, notes and method.

I used the existing script [1] that cooperates very nicely with vim.
1: https://github.com/rory/django-template-i18n-lint

Fixes #676

- No longer subclasses the auth view
- Uses a mixin for shared view functionality

- Use a FormView (as it is a form view)
- Move the redirect URL validation into the form

- Use form labels in template
- Write email errors next to form field

Before, it was possible to enter an existing email address and continue
the checkout process as a guest, which is a bug. It was also possible to
select to create a new user, but the then-displayed form would disallow
creating a new user with that email address.

All code handling email addresses has been update to use a new function
normalise_email, to have one consistent way of handling email addresses.

This function lowercases the domain part of an email address if it can
find an @, so it works on partial addresses as well.

The assumption is that most customers will not have an account (unlike
Amazon, eBay etc.), hence the default is to create an account.
The wording has been changed to hopefully be more approachable.

When you use the notation with slashes, use full path to file.
With dots, enter module name. Commands run with the current test set.

A check in ProductForm's __init__ caused an error when the parent field
is not present. It is reasonable to believe that this field would be
omitted for deployments that sell only canonical products. Hence, the
existence of the field is checked before altering it.

The get_object() caching was slightly confusing. It's been streamlined
and it's usage hopefully is a bit clearer.

- Only handles Datacash payments at the moment

- Fix payment event reference issue
- Upgrade django-oscar-datacash
- Handle changes to bankcard obj

- Add new block for payment tab
- Rename transactions block
- Provide transactions in get_context_data
- Better handling of empty iterables

- Also rename field to display_order as that makes more sense.

This should help protect against faulty migrations.

The backported version didn't explicitly create the ProductAttribute
instances before assigning and so they didn't save.

Conflicts:
	docs/source/releases/v0.6.rst
	oscar/apps/order/processing.py
	oscar/templates/oscar/dashboard/orders/line_detail.html
	oscar/templates/oscar/dashboard/orders/order_detail.html

Faster tests are faster.

This is done by staticfiles' runserver command automatically.