Added model state validation for Create/Update
Updated Cookie Id property to UserId. This was causing model binding issue since Product model also has Id property. Similar kind of issue is blogged here
http://www.hanselman.com/blog/TheWeeklySourceCode38ASPNETMVCBetaObscurityModelStateIsValidIsFalseBecauseModelBinderPullsValuesFromRouteData.aspx
Updated view to display model errors