Allow Deal date ranges.

The discount feature for wholesale clients is very limiting. We often give promotional pricing for a certain time/date period and it would be great to have this ability to load a deal against a certain product a customer gets for a date range (so that any purchases, against that product, with in the date range automatically get discounted. Once date range is complete the deal automatically expires. The current set up is prone to human error if Management forget to remove discount from product.