Add Zend\Stdlib\Hydrator\Strategy\ClosureStrategy

Example of use:
$hydrator->addStrategy('category', new ClosureStrategy(
    function(Category $value) {
        return (int)$value->id;
    },
    function($value) {
        return new Category((int)$value);
    }
));
Merge branch 'hydrator_closure_strategy' of git://github.com/bondvt04/zf2 into feature/3230
[#3230] CS fixes

- Trailing whitespace
Merge branch 'feature/3230' into develop

Close #3230