[PO] BPA Price Break - Discount (%) field

It is a field to display percentage of discount applied to the new price compare to the very first price.

For example,

Break Price for line 1 = $100, line 2 = $80, line 3 = $70

Value for Discount (%) field fo line 1 = 0, line 3 = 20, line 3 = 30