Copy Lines from CRM should track custom prices

When you copy quote lines from a CRM quote to the clipboard, it would be useful to store whether the price has been amended from the standard sell price. This uses the "sellpricetype" flag or S or C.

Currently, if you have a quote with custom prices, and you copy quote lines to clipboard and then paste into another quote, any changes to the quote line will recalculate pricing as the sellpricetype is set to S instead of C.