Increase the simple code field for inventory items from the current limit of 20 characters to 50

Increase the simple code field for inventory items from the current limit of 20 characters to 50

We need to be able to produce meaningful stock codes containing a code to describe product specification, this requires more than the current 20 character limit. We are prepared within reason to fund this development as we see it as a fairly simple change since the SQL database can handle 400 characters and the stocklink field is used to cross reference to other databases so this should not affect any other processes within Sage Evolution.