finish transition to newer /usr/bin/i18n (haserl-based) form & allow translations for digital information units

haserl-i18n: provide symlink to /usr/bin/i18n
quotas_template, reboot.sh & openvpn_upload_client.sh: transition to newer i18n shell format
localize.py: update for newer i18n format

digital informational units externalized. This fulfills one of Cezary's request here: https://github.com/ericpaulbishop/gargoyle/issues/194