Adds "Sell Price per unit" to the tooltip of item stacks.
Extra features for classic:
- Shows the sell price even while not at a vendor (just like Vendor Price, Leatrix Plus or BetterVendorPrice).
- Always shows the "Sell Price:" label prefix even while at a vendor.
- Always shows the "No sell price" label if applicable.
- Recipes: Always show the sell price at the bottom of the tooltip, even while not at a vendor. Tooltip additions by other addons get placed below this.
- Bagnon: See the correct prices for cached stacks (i.e. when looking at bank items while not at the bank or when looking at inventories of other toons).
