Add Utilities::tidy_dir sketch

This sketch is ideal for dropping in place to clean up old log files as
they age. the demo.json params give an example of how to call this sketch
for cleaning up the /var/cfengine/outputs directory.
changed days_old disable value to null from "-1"
remove left over option from README template
Merge remote-tracking branch 'origin/feature-utilities-tidy_dir' into work-fix_aptrepo