- Add usage message on argument mismatch where available
- Remove unused message keys
- Create tool task to search for a message key's usages and to find unused keys
- Remove 'reg_voluntarily'
- Remove 'user_unknown' in favor of 'unknown_user' - but move text from old 'user_unknown' to 'unknown_user'
Found by @Twonox
Part 1:
- Use only one message entry for "Please register", that may have to be adapted to reflect the proper /register arguments
- Remove other message entries from code and from the messages files
Breaking change: reg_email_msg is also removed
