Transparent Proxy.
This convenience extension to ProxyServlet configures the servlet as a transparent proxy.
The servlet is configured with init parameters:
- proxyTo - a URI like http://host:80/context to which the request is proxied.
- prefix - a URI prefix that is striped from the start of the forwarded URI.
For example, if a request is received at /foo/bar and the 'proxyTo' parameter is "http://host:80/context"
and the 'prefix' parameter is "/foo", then the request would be proxied to "http://host:80/context/bar".