Now you can type commands into each mini-console!

The console tool spawns and monitors a bunch of nodes.

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.

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.

Also remove all non-object-oriented legacy Mininet code and update
tests.

User-space compatibility is untested, but most of the code for it is
still in.

Nodes include Switch, Host, and Controller; move these to a separate
file.

This file still could use some attention to hide private functions.
Node seems like a primary class to extend, for adding stuff like Open
vSwitch, so it could benefit from a simpler interface.

Having a file with the same name as its package creates hard-to-diagnose
import error, so rename mininet.py to net.py.  This commit moves utility
functions, generally those dealing with network namespaces and interface
management, into their own file.

Also fix a few minor formatting bugs and clean up logging code (which
had issues when multiple files would import mininet.logging_mod).