Mod #1379 Changes for Promotions & System Option #195

This modification works with entree System Option #195 to support the Promotions feature it activates.

It makes these changes in Create/Change Invoice:

Add a "Net Unit Price" column, which is the "Unit Price - Promotion".

Update the "Extended Amount" column to be calculated using the "Net Unit Price" instead of the "Unit" Price".

Add 2 fields in to the footer "TPA" - total promotions available and "TPS" - total promotions saved (withheld).

Change the "Total Promotion" label to read "TPG."