[ADD] CDN support for website
[FIX] product: remove empty from state field selection

In order to avoid having twice "empty" in the web client. There is always an empty option in selection field in the web client. When the selection field is required, you have to select it, and it is not required, you can set False as selection value
[IMP]Sale:In contract add stat button for total invoiced and due invoice amount and if an invoice is due, the contract should become pending,in the task/issues, show the alert.