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.

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.

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

Now you don't need to specify a default read count.

Now, by default, we print the pid out in sendCmd() which allows us
to snarf it later and set lastPid correctly.

Now, we wrap os.kill() in a try block, so that if the process is
already gone we don't get an exception.

This reverts commit 07aad110.

When the semantics are clear, functionality like this will get added back to
Mininet.

Conflicts:

	mininet/node.py

Controllers are no longer namespace-able, and all calls need one fewer
arg.

Also use more sensible temporary variable name.

We should check NOXController and RemoteController to make sure that
they are not broken, but I cannot do this at the moment.

It should also probably be renamed to something like:
configLinks(src, dst, status).

Moved monitor() and readline() into net.py and node.py respectively,
which will hopefully be useful for monitoring large sets of hosts,
as is done in udpbwtest.py.

Changed iperf to use interactive command infrastructure (such as it
is), which may make it more reliable. Hopefully it's a bit clearer
as well, although it is slightly more complicated.

It seems easier to rely on node.waiting for the moment.

Before this commit, you'd have to manually insert the kernel module for
OVS or OF kernel modules, and you couldn't run one regression test with
all 3.

Now, these are kmod insert/remove is handled automatically.

I've changed the way things work a bit:

1. netns is replaced by mnexec, a general-purpose mininet helper.

2. For interactive commands, we now use mnexec -p, which prints out
   the pid, so we can kill it when someone hits control-C!

3. We close file descriptors for subshells. This might save memory,
   but who knows.

4. We detach our subshells from the tty using mnexec -s; thus
   control-C should not terminate everything.

5. Given 4, mn -c is now necessary if you kill mininet.

Close to solving this set of problems.

Call netns using setsid to detach from the tty; this is
intended to fix the problem of control-C killing your network.

sendInt() doesn't actually work - hopefully we can fix this in the
future, but it's tricky since we want to detach the many shells from
our tty, but then optionally send tty interrupts to them! Ideally we
would either know the pid of the subprocess or be able to send a signal
to bash to get it to interrupt its subprocess.

waitOutput() now uses monitor. We also handle sentinels
coming in the middle of output (but default at end should
still work well.)

Call netns using setsid to detach from the tty; this is
intended to fix the problem of control-C killing your network.

sendInt() doesn't actually work - hopefully we can fix this in the
future, but it's tricky since we want to detach the many shells from
our tty, but then optionally send tty interrupts to them! Ideally we
would either know the pid of the subprocess or be able to send a signal
to bash to get it to interrupt its subprocess.

waitOutput() now uses monitor. We also handle sentinels
coming in the middle of output (but default at end should
still work well.)

We need to figure out how to specify the IP addresses for the
routed control network. For now I'm going back to 192.168.12x.y

Also changed controller params to use IP strings rather than
numbers. However, we still need to clarify what ControllerParams
is actually for.

Also changed the str format for nodes to use str() rather
than repr() so we don't end up with extraneous quotes.

Also tweaked cmd/cmdPrint to make them more beautiful and functional,
and a few other minor changes, such as using a new idiom for verbose.

These changes support reinstating the examples.

This increases flexibility by allowing a topology to be manually created
in Python, or specified using another format, without having to create
a Topo object first.

However, Topos are useful, and are still the default topology object!