Cleanup of doc files.

Fixed xterm.py (and cleanup) to clean up screen sessions.
Cleaned up sshd.py (though interface is still in flux.)
Added 1024-node network example (treenet1024.py).
Added example showing multiple tests on a single network (multitest.py).
Renamed examples to make them easier to type!

examples/multitest.py

@@ -0,0 +1,14 @@
+#!/usr/bin/python
+
+"Run multiple tests on a network."
+   
+from mininet import init, TreeNet, pingTestVerbose, iperfTest, Cli
+
+if __name__ == '__main__':
+   init()
+   network = TreeNet( depth=2, fanout=2, kernel=True )
+   network.start()
+   network.runTest( pingTestVerbose )
+   network.runTest( iperfTest)
+   network.runTest( Cli )
+   network.stop()