CSV upload - use alternate reference/SKU in place of Product ID

It would be useful when using the CSV upload to be able to use the Product Alternate Reference 1 field instead of the Product ID such that if you had a CSV to upload which had a list of products where the code is actually the Product Alternate Reference 1 field and uploading that will match it against the Product ID and allow you to add those products with the relevant alternate reference fields to your Quote.

As we're looking at adding an additional SKU field for Unleashed/other newer integrations, we should consider that field for the CSV upload too