WL-172 Show a Order History list on the Student Dashboard for any PaidCo...

...urseRegistration or RegCodeItem that the user might have purchased
1) I'd prefer that this code live in `shoppingcart`, since it needs to know a lot about the shopping cart models.  One possibility would be to add an `api.py` module in shoppingcart, and add an `order_history` function with this logic.  This function could accept kwargs for the course org filters.

2) I'd like to see donations and verified certificates included in these results, unless there's a good reason not to.