Introduce Zend\I18n\Filter\Number based on Zend\I18n\Filter\NumberFormat

This PR is related to https://github.com/zendframework/zf2/issues/4493 and replaces https://github.com/zendframework/zf2/pull/4495 and introduces `Zend\I18n\Filter\Number` which filters a string parseable by `NumberFormatter` to a number.

Ping @cgmartin.