* New attribute on product class
* Optimised checkout for digital goods

This is needed for internal Tangent projects.  The search app in oscar
still needs some work but it works in a very basic fashion at the
moment.

The template for search results still needs attention.

This avoids conflicts with other libraries that use the same trick for
extending templates.

Plus tweaks to test method names

Also split them into unit and functional tests.

- Tidied up JS slightly, using 4 space indentation
- Moved layout_* templates into folders
- Few updates to the base templates
- Put oscar's JS into its own folder within static/js
- Added flatpages to the test env to get tests to pass