Add JsonSerializable polyfill for PHP versions less than 5.4.0
Enhance Zend\Json\Encoder to encode JsonSerializable classes
Merge pull request #4534 from gwis/feature/jsonserializable-polyfill

Introduce JsonSerializable polyfill and support in Zend\Json\Encoder
Merge branch 'feature/4534' into develop

Close #4534
Resolves #4507