Provide separate Promise date and need by date on PO when BMT=No

Summary:

In a constrained supply plan, the suggested due date which maps to a Purchase order promise date is determined by the Lead Time. The need by date is calculated by planning based on the demand. We have need to provide both fields on the Purchase order to the supplier. The Original Promise date is based on the Lead time from the supplier and the need by date is based on the current demands. BMT flag is No. This allows us to communicate when we want to receive the material