Raw network handler

Raw handler now parses an optional json file with the network interface information, and emits network stats.
Hmmm this is the only part of this patch that makes me uneasy. This really should be the full container name. I'm guessing you are wanting to use the Docker ID? I'm also guessing you're not using systemd? Would it be too much trouble to go with /docker/<id>?

I don't want us to have to do this matching since it lends itself to incorrect collisions.