NumberConverter does not observe NumberFormat's parsePosition

When parsing numbers with java.text.NumberFormat, it is important to observe the ParsePosition.

If, after parsing a number, the parsePosition is less than the length of the input string, this actually means there was a problem. Example:

With grouping disabled, the String "0,23" is parsed to 0, and the parsePosition is set to 1. This should be considered as a parsing error.