Add Purchase Order Change Orders Merged

There needs to be a way to enter a change order against a purchase order. If the amount of the purchase order has changed or new lines have been added, the users need a way to know what the original vs revised amount is. This also needs to export to sage intacct. Right now if a purchase order needs to be changed, you have to edit the PO in SCM, then you have to go into sage intacct and try to update it in there, or delete it from Intacct and reexport it. This is not possible if the PO has already been converted to an invoice.