Mass price recalculation

[einhverfr]

via @pongraczi
Mass recalculation also would be nice:
imagine an imported product list, where the purchasing price in USD, but selling price is HUF (EUR, whatever) -> as the exchange rate is changing, it would be nice to adjust the price.
Example: adjusting by percent or fixed amount.
Original price: 100
Increasing it by 10% -> new price: 110
Increasing it by adding 20 -> new price: 120

[ehuelsmann]

Instead of the proposed solution, a "price update upload" would be a very flexible solution: the price update could be done in a spreadsheet while the complexity of LedgerSMB stays low.