(In user, kernel and ovsk switch classes.)

For some reason, the leading spaces were missing.

On debian, the module blacklist is blacklist, not
blacklist.conf.

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.