Adjust importing of models for factories

Using get_classes for models isn't the right way.
Docs: Add note on unsupported Django admin
Docs: Add notes on migrations with a custom User model

All credit for those findings goes to Dawid Lorenz.
Add docstring to dashboard's IndexView

Without it, Sphinx' autodoc for oscar.apps.dasboard.views would not
list the view nor it's members.
Docs: Cross reference dashboard navigation how-to.
Docs: Fix several syntax errors

* Use correct directives in signals.rst
* Removed newline in glossary.rst that broke sorting of glossary terms
* Removed syntax warning for upgrading.rst
Extend basket line with stockrecord field
Adjust bankcard model to provide an obfuscated number property

Useful in templates where the bankcard form is rendered.  Eg:

    {{ bankcard_form.bankcard.obfuscated_number }}
Slight tidy of checkout to better support billing addresses
edited typo in sandbox.rst
Tougher tests for category browsing

Verify that a correct URL leads to no redirect, and verify that an
incorrect URL leads to a redirect and the redirect has the correct URL.
New URL scheme for permanent category URLs

The old one was too identical to the product URL scheme and caused
issue #765. There really isn't a good way to keep them in the same
"namespace", hence all category browsing will happen under
/catalogue/category now.
Change data migration to act on frozen orm model instead of using call_command
Run tox tests in parallel with detox

Faster is better!
Docs: Correct a few minor mistakes
Suppress debug output of template timings debug toolbar panel
Add introspection rule for UppercaseCharField

This is necessary for South migrations. As it doesn't define any new
parameters, an empty ruleset is all that is needed.
Contextualize address title

A product's title is different from a person's title. Needed e.g. for
translating to Portuguese.

Fixes #667
Add missing migration for UppercaseCharField on AbstractAddress

I wasn't aware that this change requires a migration. But South reports
it, so let's keep South happy.
Add another missing migration for UppercaseCharField

Unfortunately, abstract versions of addresses are located in the address
app, but then used in e.g. order/models.py. That's why I missed the
migration for this one.

Oh well, all good things come in three's!