Add base path to prerender url

This parameter is useful when in your internal infrastructure, the network traffic go through one endpoint ( ip or host ). Ej:

http://mycompany.servers.com/app1/service1/....
http://mycompany.servers.com/app2/service1/....
http://mycompany.servers.com/app3/service1/....

It would be very nice to be able to set something like:

http://mycompany.servers.com/prerender/http://www.....