Pass session to script

[igorw]

Not sure if this is of any use, but to properly share the session object, it could be serialized and passed through env and headers:

[CgiHttpKernel Session] --- CGI --> [Child script Session]
                                               |
                    [serialized env var]       |
                                               v
[CgiHttpKernel Session] <-- CGI --- [Child script Session]

                [serialized response header]