[#zf3617] New DateTimeNormalizer Filter

This PR introduces a simple `DateTimeNormalizer` Filter class that will attempt to format a provided string use the specified date() style format.

The main advantage of this is to allow pre-formatting of a provided datetime value on a `Zend\Form\Element\DateTime` where the HTML5 spec and different browsers may pass values with or without seconds which can cause the validator to fail.

The default format string for the `Zend\Form\Element\DateTime` is now the standard \DateTime::W3C.

Tests to follow sanity check by CR review team. There is no BC break.