Added inverse Attribute to ProductGroup.

BillInventory Renamed.
Refactored Bill to be more usable.
Added Bill Detail Report.
Added Open Bill and Bill Details Roles.
Zero Rate Products have Yellow background Color.
Refactored UserBI, FoodTableBI, ModifierBI, PrintLocationBI, ProductBI, ProductGroupBI, TaxBI, UserBI,
Cached the Products List.
Product and Product Group Form Working.

Tanshu.Accounts.Contracts/Data Contracts/ProductGroupBO.cs

@@ -18,6 +18,7 @@ namespace Tanshu.Accounts.Entities
         public virtual decimal DiscountLimit { get; set; }
         public virtual bool IsModifierCompulsory { get; set; }
         public virtual string GroupType { get; set; }
+        [Inverse]
         public virtual IList<Product> Products { get; set; }
     }
 }