Add possibility to specify number of decimals for \Zend\I18n\Filter\NumberParse

Here is the pull request
please use psr-2 cs for conditional  https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-2-coding-style-guide.md#11-example and the indenting https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-2-coding-style-guide.md#24-indenting