#1075 Alllow consolidation of PO from Req. with different dates

[FreePath]

When generating PO from requisitions, more then one requisition can be consolidated into one order.
One of the parameters used to decide if a new order is to be generated is the DateRequired field of the requisiton line, so if two lines have different DateRequired, this will result in two different orders.
Since the DateRequired is present on the order line, in some situation is preferred to generate a single order, with different DatePromised specified at line level.
A parameter may be used to decide if the DateRequired is relevant at order level.