i18n formatting and Japanese language strings for MsgText.py

[ericthebell]

Japanese localization

This code is intended to (1) implement a format for each message to strings for multiple languages, and (2) provide a set of Japanese translated strings.

Checklist

• I have read the contributing doc.
• I have included a link to the relevant issue number.
• I have checked to ensure there aren't other open pull requests
  for the same issue.
• I have written new tests for these changes, as needed.