I had thought we wouldn't need this but it turns out you do in order to
consume/cancel stock allocations through the order EventHandler.

- Only handles Datacash payments at the moment

This is useful for linking between payment events and transactions.

- Add more links
- Add event details to line detail page

This is for checking if any line has passed a given shipping event.

This is useful when validating potential shipping events.

when trying to perform order management events.