Add a db-statement-timeout option for postgresql sources Use that new option to set the statement_timeout option when creating connections, except for maintenance operations (shell and upgrade). Closes #2547026

usr/bin/cubicweb-ctl usr/bin/
usr/lib/PY_VERSION/*-packages/cubicweb/cwctl.py
../cubicweb-ctl.bash_completion etc/bash_completion.d/cubicweb-ctl