Added Combo Discount

This update adds combo discount.
Run "DB - Update 4 - 2014-04-26.sql before attempting to do anything
else
A table is added that will define the menu item to be added as part of a
combo. in combodrinkmenuid put { storeid, menuitemid of the item to be
added, discountamount}

Additionally a "Discount" menuitem is added with unassigned category and
the price of 0. this is used when applying discounts and particulairly
the combo discount.

when a user adds an entree they are prompted to add a combo if the order
is eligable to have a combo added. Then the item that is specified in
the table above is added (at regular price) then an additional "Combo
Discount" item is added that gives the discount specified in the table
above.
Merge branch 'master' of https://github.com/bmsmith/NSA-Sandwich

Conflicts:
	CustomerInterface/CustomerInterface.v11.suo
	CustomerInterface/CustomerInterface/NSAConfig.xml