Added "VAT Registration No." field to sales quote, order and invoice pages

It is now possible to fade in the field "VAT Registration No." in the Sales Quote, Sales Order and Sales Invoice pages.

The field is editable and if it's changed the "VAT Registration ID" of the customer gets updated. Depending on the customer used for the vat calculation the Bill-to or Sell-to customer is updated (see setup "Bill-to/Sell-to VAT Calc." in G/L Setup).

If one forget on the initial setup of the customer to setup the "VAT Registration ID", by this change it is easy to add it via existing documents.