Extend Unicode Number Formatting Validation

The current functionality implementing Number Format Validation does support the [padding](http://www.unicode.org/reports/tr35/tr35-numbers.html#Padding), [rounding](http://www.unicode.org/reports/tr35/tr35-numbers.html#Rounding) or [significant digits](http://www.unicode.org/reports/tr35/tr35-numbers.html#sigdig) functionality.

This functionality should be added at some point.