Locale support for number formats

This change adds a number-formatting-support based on the users language-setting.

*P.S.*

ZF2 would support that feature out-of-the-box with the ViewHelper *NumberFormat*, but it uses the php-extension intL (http://php.net/manual/en/book.intl.php).  So I implemented the feature this way, because I didn't want to add a (new) dependency.