[Shipping] Remove hard coded shipping costs from the language files

[panigrc]

This will be a greater refactoring as anticipated.

In order to provide the option to the user to choose among the shipping and billing methods, the options must be defined either in the Database or in the configuration.

Additionally in the Order table the fields

• shipment_express
• shipment_to_door
• shipment_cash_on_delivery

must be removed

And replaced by the following

• shipping_method
• payment_method

Another proposal would be to add 2 additional tables payments and shipments linked with the order table by using an one to one association i.e. with fields shipment_id and payment_id.

In this way we could expand the payments and shipments later for example with shipment status and payment status.