Print barcodes.  Adding parts now more intelligent

• Checks if keyed/scanned barcode is same as highlighted part.
• Performs canonicalization of parts as per point of sale (i.e. strip leading 0s, follow supercessions)
• Checked if keyed/scanned barcode has not already been added to barcode list)

Visual tweak to setup screen. Last update included an option that was visible on all tabs : should of only been visible on spares 2 tab.