Add support for Money field in commerceCurrency filter

[rynpsc]

It would be nice to be able to pass an instance of a Money object to the commerceCurrency as well as a float to take advantage of the same formatting and currency conversion.

At the moment as far as I can tell a number field still has to be used if you want to pass the value to commerceCurrency. It would seem intuitive that a Money field could also be passed to a currency filter.

{{ element.myMoneyField|commerceCurrency(cart.paymentCurrency, true) }}