Add sticky session support

In accordance to this [http://www.iamjambay.com/2013/10/a-quick-tour-of-cloud-foundry-router.html](http://www.iamjambay.com/2013/10/a-quick-tour-of-cloud-foundry-router.html) i think it's better idea to change `PHPSESSID` by `JSESSIONID` . It will permit to never loose session in multi-instance php website.
Don't you think?