set limit on how large of a resultset Clark will build graphs for

set limit on how large of a resultset Clark will build graphs for

Attempting to draw a bar chart on a 50,000-row result set
can consuming system resources for no particular purpose, so
by default Clark Kent will now refuse to generate a bar, pie, or line
chart if the resultset has more than 1,000 rows.  That limit
can be adjusted using a new command-line paramter for clark-kent.pl,
--max-rows-for-charts.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>