Added ST Number to bill.

Fixed error were unprinted bill was not removed from table when voided.

Tanshu.Accounts.PointOfSale/Controllers/BillDict.cs

@@ -0,0 +1,12 @@
+using Tanshu.Accounts.Contracts;
+using Tanshu.Common;
+
+namespace Tanshu.Accounts.PointOfSale
+{
+    public class BillDict : OrderedDictionary<BillItemKey, BillItemValue>
+    {
+        public delegate void ItemChangedHandler();
+        public event ItemChangedHandler ItemChanged;
+
+    }
+}