ibtop: Add missing common.h file

common.h provides the well-known likely()/unlikely() macros.
ibtop: Sort nodes by bandwidth

The current code version uses the order of the nodes as obtained
from libibnetdiscover. In order to increase the visual
representation of the fabric load this commit modifies the code
such that nodes are sorted according to the maximum tx/rx bandwidth.
In order to avoid unnecessary jitter the node order is kept fixed
over a period of window updates (10 in the current setup).
ibtop: Improve data representation

This commit adds additional vertical bars for seperation, units
and the percentage sign to each line in the output.
ibtop: Change line formatting

This commit replaces "%-10g" by %10.2f" in the formatting
of output lines.