Added support for X-Forwarded-Proto https headers.

When https requests are transferred from AWS ELB (load balancers) they are returned as http with the original scheme encapsulated in a X-Forwarded-Proto header. I have added support for the X-Forwarded-Proto header and for both https schemes together. This will allow a https response to be directed to the secured content when the server is part of a cloud solution behind a load balancer.