Fix thousands separator

[igitur]

Found a case that isn't handled correctly with regards to thousands separator. Hope you agree with this fix.

public void TestThousandSeparator()
{
    var actual = Format(1469.07, "0,000,000.00", CultureInfo.InvariantCulture);
    Assert.AreEqual("0,001,469.07", actual);
}

[andersnm]

Thanks, nice find! The fix looks correct, but a minor nitpick: I would prefer without the Token.IsSignificantPlaceholder(string token) helper, and replace with c == "0" directly in the modified if-clause. Could you do that too please?

Because there's a couple other places testing against "0", "?", "#" etc for similar purposes, and their meanings are kind of assumed implicitly from the context. It's definitely a good idea to replace these hardcoded strings with constants globally and consistently at some point!

[igitur]

Changes made and rebased.