Start/stop LINC network elements from Mininet

For instance, if we want to bring down an optical port, we first need to deduce LINC-OE switch number (these are not the same as Mininet's, although the port numbers are identical), then open up a LINC console, and finally bring down the port with a less than user-friendly command. Ideally, we simply want to bring down the port in Mininet.

We want this for all network elements: switches, ports, and links.