Add i8n

[yorickdowne]

See https://tiswww.case.edu/php/chet/bash/bashref.html#SEC13 and https://www.linuxjournal.com/content/internationalizing-those-bash-scripts

Default path in Linux is /usr/share/locale and then the language

• Mark all strings to be translated with $"text"
• Create ethd.pot file
• Make language.po file
• Compile into .mo file
• Copy to language/LC_MESSAGES/ethd.mo in /usr/share/locale by ethd update and ethd install
• Set TEXTDOMAIN in ethd