cron_period_dir - Prints the cron script directory for a given period ($1).
cont_script_file - For a given cron period ($1) and name ($2), prints
the filename for installing a new cron script.
cron_script_write - For a given cron period ($1) and name ($2), writes
stdin to the appropriate cron script file as root.
cron_script_init - For a given period ($1) and 0 or more command verbs ($@),
creates a cron script that calls the current script's 'cron run' command.
Additional command verbs are used to create a unique script name and
passed as additional arguments to 'cron run'.