CORS Filter

CORS header management to allow REST Api support Cross Origin Resource Sharing.

Supported input headers :

* Origin 
* Access-Control-Request-Method 
* Access-Control-Request-Headers 

Supported output headers :

* Access-Control-Allow-Origin
* Access-Control-Allow-Method
* Access-Control-Allow-Headers
* Access-Control-Allow-Credentials
* Access-Control-Max-Age
It overwrites `$this->request` even if it's set by user.