Bug fixes relating to ongoing regression defects with refunding spares caused by UOM and consolidating invoice/refund

• Allow -ve freight on point of sale complete for freight refunding
• Point of Sale tender display : make it visually obvious when displaying result of a refund
• Point of sale: provide visual clues on what to do in order to refund an item (i.e. -ve qty)
• Point of sale: when a qty is to be refunded always default restock to qty refunded. User must override all changes here if not being restocked

Other things in play:

• Added some infrastructure to support upcoming new feature: ability to key in unit details on a web enabled mobile device. (i.e. copy vin details etc from the bike using a tablet or mobile phone). Nothing functional yet. Hopefully in a few weeks.