loadbalancer: Terminate SSL in the HAProxy loadbalancer.

This commit allows deployer to define if they want (per API) the SSL
to be terminated in the HAProxy or not.
I think we shall set the "option forwardfor" by default, because if we don't, every backend will see only the haproxy's IP address (in case of ssl-offloading), not the real client's one. This option adds the well-known X-Forwarded-For header.