Cookie Domain Not Copied

[mkueng1]

In ProxyServlet.copyProxyCookie() there's a comment

don't set cookie domain

Why is that? In my case I need this.
Would you agree to have a parameter to enable copying the domain? Of course it only makes sense when the domain is part of the used host.

[dsmiley]

I worked on this a long time ago but, yeah, I figured the domain isn't necessarily the same host so it's unsafe to set the host. Feel free to propose a PR.