set a limit on how long a Clark Kent query can run

set a limit on how long a Clark Kent query can run

Reporter queries that take too long to run are very often
simply malformed, and in extreme cases can chew through
a lot of temp disk space on PostgreSQL servers.  To avoid
this, Clark Kent by defaults only allows a query to run
for up to 10 minutes by setting a local statement timeout.

The value of the timeout can be tweaked by setting the a
new command-line option for clark-kent.pl, --statement-timeout.

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