Use the juvenile setting when removing juvenile flag.

Use the juvenile setting when removing juvenile flag.

When calling the API open-ils.storage.actor.user.juvenile_to_adult, most notably
from the juv_to_adult.srfsh support script, instead of strictly using the
hardcoded passed value, first check the global.juvenile_age_threshold from
the settings based on the users home library. If the setting does not exist,
then fall back on the hard coded passed value.

This will allow each library to be able to set different juvenile thresholds
if needed and at the very least, give control to the settings rather than
rely strictly on the hardcoded passed value.

Signed-off-by: Steven Callender <stevecallender@esilibrary.com>