Minor cosmetic change, really.

Note now that we can pass options into switches; for example,
we could enable stp with Switch( 's1', opts='--stp' ).

It seems that it is more convenient to be able to call

cmd( 'foo', 'bar', 1)

for example. However, this may make it slightly less
efficient, so we will see how it works.

Link check wasn't quite right - e.g. 'eth1' could be found in
'eth10' previously.

Updated quietRun to allow passing in args directly rather than
as a list.

I'm still not 100% sure on this.

It may be fragile, but it does sort of work.

This allows monitor() to be used for polling. Of course, you
probably want to use poll() first anyway, but it's nice not
to have to block if there's no output.

This is not as generic as having a single 'term' command, but
it's a lot more convenient to use.

This should make it easier for people who use screen for other purposes
to identify which sessions were created by mininet.

We may still need additional code to clean up after ovs.

There might still be some issues with this however...

For a network, we create "links" rather than "edges" on a graph.

"Edges" is a bit confusing because the links may not be edge links on
the network!

Also, since you're not necessarily running a "test", I changed it to
just say that we're "Done."