Dynamic Pricing

Allow dynamic pricing to offer gloabl discounts for value and quantity.

Currently the gloabl discount function is on value only.
It would be a very simple change to a parameter to allow for volume.

eg buy 10-20 books, get 5%
20-100 get 10%
etc

I was suprised to see that the pricing was so dynamic that it only allowed for this within categories and not globally and this does not work with our current discount structures.