We add a new form to the profile section that requires the customer to
confirm their password, but which then deletes their user.

ClientTestCase is deprecated.

Fixes #826
Fixes #1007

The locations of the form to re-order an order has changed, so the tests
needed updating.

This allows updating code in both places, if necessary. Getting Django
1.5 support would be painful otherwise. This also removes the circular
dependency of django-oscar-testsupport on Oscar.

The requirements were merged. The imports were updated
accordingly. Unused imports in the touched files were removed. No
further changes.

The AccountSummaryView was trying to do too much and included random
bits from the other views. It has been changed to a simple
RedirectView. The redirect target can now be set with
OSCAR_ACCOUNTS_REDIRECT_URL and defaults to the newly-introduced
ProfileView. This leaves the UX unchanged apart from the fact that
was used to be scripted tabs is now separate views.

There was a lot of template duplication between the separate views. I
have introduced a PageTitleMixin and used this to significantly reduce
redundancy (e.g. hundreds of lines). This also led to removing a few
slight inconsistencies regarding headings, breadcrumbs etc.

The new templates have been categorised in subfolders.

Apart from the new ProfileView, I've had to introduce a simple
ProductAlertListView. I've also upgraded the ProductAlertCancelView to
be useful for both canceling from emails etc. as before, but also from
the ProductAlertListView.

The profile test can_change_password checked if the password change
form can be submitted succesfully, but did not verify that Django's
authentication system accepts the new password.

Fixes #376

A user in Oscar is identified by email address instead of the
username. This is, however, not set as a ``unique`` constraint
in the user model in ``django.contrib.auth.models.User``. Checks
if an email already exists are carried out when a user registers
but are ignored when a registered user changes their
profile. This can lead to multiple users having the same email
address which should not happen.

I provide a failing test with a mixin that can be used in both
the ``UserForm`` and ``UserAndProfileForm`` to clean the email
field when validating the form. A ``ValidationError`` is raised
when a user with this email address already exists and is not
the currently edited instance (makes sure that profile updates
with unchanged email work still).

Fixes #324

* Tests now split into more coherent modules
* Added IDs to forms to help WebTest
* Some refactoring along the way