Restored scratchnet and scratchnetuser demos.
Also changed the str format for nodes to use str() ratherthan repr() so we don't end up with extraneous quotes.
Use setuptools to install python files
Now, to reference mininet files, use 'import mininet.mininet'.
PYTHONPATH mods are no longer required for installation.
Minor tweaks and corrections.Added commentary on control network to mininet.py.Hopefully fixed linearbandwidth.py for real.
Tweaks to documentation files and sshd and xterms examples.