2559 pjax filter

Fixes #2259 issue nevertheless I would like to add that even if the current solution works, I am not sure about `pjax` library as this library is not being updated regularly, its last modification was a month a go. 

I wonder whether we should maintain our own copy as we do with libraries such as `yii.gridView.js` or `yii.js`, that way we would be able to provide solutions that doesn't workaround an issue of the external library but to the library itself.