backrunner: HTTPS support

We at develop highly scalable distributed storage Elliptics for medium and large objects. And in the web era the most frequently used API is HTTP. We had developed HTTP proxy for elliptics named Backrunner, it supports a wide range of options like ACL, streaming, redirect, partial upload/download, static file downloading and many others.

But if you build a system hidden behind HTTPS you likely want to secure your work with storage, in porticular your CDN will likely require you to work via HTTPS in this case.

So we have updated Backrunner to support HTTPS. It can listen for unencrypted and secured connections simultaneously on different ports/addresses, and you have to provide certificate/private key files.

This rather small change allows to deploy fully secured storage access to your frontend.