fully removed unnecessary unsigned > 0 check
friendlier histogram intervals with condensing

Each candidate histogram in the time histogram now has nice human-friendly
intervals.  Sometimes this means that in the worst case there may be so many
bars as to be unreadable (a day broken up into 10 second intervals).  In this
case the bars are condensed to a more readable size before rendering
de-centered port and address histograms
time histogram coloration improved

if either the source or destination port of a packet is colored, that port is
submitted to the time histogram.  This creates more consistent coloring since
both sides of HTTPS transactions are green for example.  If both ports are
colored, source and destination alternate.