Adding smart_selects app with url direct.

Signed-off-by: Rob Dobson <rob@rdobson.co.uk>
Implement a chained foreign key for restricting the selection of hotfixes based on product version.

Signed-off-by: Rob Dobson <rob@rdobson.co.uk>
Update the article model tests to provide a hotfix a product model.

Signed-off-by: Rob Dobson <rob@rdobson.co.uk>