Add Nagios output from daily-lasso

This merge request adds optional Nagios JSON output from daily-lasso, similar to the other daily automated tools:

• Add a --disable-nagios flag, which defaults to False
• Except all CalledProcessErrors, raising a UserWarning whenever a call to gwdetchar-lasso-correlation fails, and collect the return code from Lasso for each lock segment
• Unless --disable-nagios is passed, write a summary JSON file that Nagios will interpret to set red and green lights on https://monitor.ligo.org (requires a separate pull request in ligo-smashing)
• Run Lasso with a half-hour timeout, that is, kill any individual Lasso process that takes longer than half an hour
• Automatically set output_dir and summary_dir from a common basedir, since local HTML paths are automatically set

This also reduces the timeout length of daily-hveto.sh.

cc @duncanmmacleod, @alexandra.macedo