Events for entering verified flow & buying
Added refund datetime info to Orders, OrderItems

Finance would like to have info about the date any given refund is requested.

This commit adds a refund_requested_time field to OrderItem and a refund_time to Order.

When a user *requests* a refund, the refund_requested_time field on OrderItem is updated; when a user actually *receives* their refund, the refund_time on Order is updated.

Note that only the refund_requested_teim field is actually used right now; later on, when we're able to actually automate the process of actually giving users refunds, we will start usings Order's refund_time field.
Response to CR
Quick fix
Response to CR
Added alternate upsell copy flag

For waffle / split testing purposes
Added segment.io tracking
response to cr
response to cr
response to cr
Merge pull request #1744 from edx/flowerhack/feature/verified-cert-events

Events for entering verified flow & buying