allow to run protocol_mail on separate schedule than dataimporter

THBI requested to receive dataimporter mails only twice a day. Implementation:

• add hisinone::dataimporter/mail_protocol/cron_term to hiera
• if this key is set: generate cron according cron entry
• use timestamp from a file (/var/spool/dataimporter/last_protocol_mail?) as start time
• write new start time after run to file
• if the key is not set: use same behavior as now.