Raw network handler

Raw handler now parses an optional json file with the network interface information, and emits network stats.
I think it should not return an error (return containerHints{}, nil). All functions that call this check the error first, if that exists they assume the operation did not succeed. I'm guessing that's not what we actually want. The file not existing is not an error, it is expected in all systems that don't provide hints. I'm arguing that this function should handle that and return a nil error.