- Remove outdated material relating to old versions of Django
- State that Oscar assumes that the email field is unique
- Update a number of links to Django documentation.
- Minor fixes to other bits of documentation.

Since there is no demo or us site anymore we can simplify the structure
somewhat by moving the sandbox one directory up

This is pretty much what I use for bikepartsmarket.com. If this gets
some more eyeballs, it might mature enough to move into Oscar core.

Just crossing items off my bucket list.

It's a nice app to handle non-blocking email sending.

Those documents lived in ref/, but really aren't reference documents.
Topics/ is a more appropriate place for them.