Juvenile-to-adult batch script

The batch juv_to_adult.srfsh script is responsible for toggling a patron from juvenile to adult. It should be set up as a cron job.

This script changes patrons to adult when they reach the age value set in the library setting named "Juvenile Age Threshold" (global.juvenile_age_threshold). When no library setting value is present at a given patron’s home library, the value passed in to the script will be used as a default.