Major refactor of the Sales Form and Bill controller to make code more readable and less error prone.

The functions now only do one thing.

Tanshu.Accounts.Contracts/Data Contracts/VoucherBO.cs

@@ -15,17 +15,17 @@ namespace Tanshu.Accounts.Entities
             Settlements = new List<VoucherSettlement>();
         }
 
-        public Voucher(User user)
+        public Voucher(User user, Customer customer)
             : this()
         {
             this.User = user;
             VoucherType = VoucherType.Regular;
+            Customer = customer;
         }
 
         public Voucher(User user, Customer customer, FoodTable table, bool printed, bool isVoid, string narration)
-            : this(user)
+            : this(user, customer)
         {
-            Customer = customer;
             Table = table;
             Printed = printed;
             Void = isVoid;