[16.3.19] Added "Code" field to inventory kits and invoice items

There is another problem with the change. We sell quite a lot of items on sale or return, and the customer specifies their own code for each item. With the new change it is not possible to change the code for the particular sales quote or invoice, and there is nowhere else to put the customer’s code. Can this be changed so that the Code field is editable for the individual invoice, just as the Description field can be edited individually?