Added bno_plot.py - generate interactive 3D plot of IO blocks and sizes

Added bno_plot.py - generate interactive 3D plot of IO blocks and sizes

bno_plot.py
	[ -h | --help       ]
	[ -K | --keys-below ]
	[ -v | --verbose    ]
	[ <file...>         ]

Utilizes gnuplot to generate a 3D plot of the block number output
from btt.  If no <files> are specified, it will utilize all files
generated after btt was run with -B blknos (meaning: all files of the
form blknos*[rw].dat).

The -K option forces bno_plot.py to put the keys below the graph,
typicall all keys for input files are put in the upper right corner of
the graph. If the number of devices exceed 10, then bno_plot.py will
automatically push the keys under the graph.

To exit the plotter, enter 'quit' or ^D at the 'gnuplot> ' prompt.