Most real-world instances will use postgresql instead of sqlite so it's
better to use postgres for the tests. This also allows us to easily add
tests for concurrency issues which is not supported by sqlite

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

Example sites now sit in their own folder (sites) for easier
organisation.

Completed the models for the order package too.  Added admin files