Add Money Support

[clphillips]

Represent all pricing values as Money from Blesta\Money.

Example usage:

$fiveDollars = new Money(500, new Currency('USD'));
$fiveDollars = Money::fromString('5.00', 'USD'); // or this
$fiveDollars = Money::fromString('5.00', new Currency('USD')); // or this

$price = new UnitPrice($fiveDollars, 2);
$price-->setDescription('2 x 5.00');
$unit_price = $price->price(); // Money
$qty = $price->qty(); // 2
$tenDollars = $price->total(); // Money

$tenDollars->getConvertedAmount(); // 10.00
echo $tenDollars; // 10.00

Any value that supports float should support Money, and convert to Money internally if provided with float. Should use the XXX currency code (which denotes no currency), where the precision is out to 4 decimal places. For example:

$price = new UnitPrice(5.00, 2);
$price->price(); // Money 5.0000 XXX
$price->total(); // Money 10.0000 XXX