Update buysell.simba

Updated several functions, Close_Shop (now resembles CloseBank), ShopItemBoxCoords (doesn't generate an extra box on the shop screen), ShopItemCoords (cleaner/clearer), BuyCoords (logical and uses proper 1, 5 or 10 options), SellCoords (same as BuyCoords, except for selling).  Also updated the Broken functions, FindItemsArray and FindItem, to FindItemEx and FindItems.