Unicodify guitranslations.py

Some non-ascii characters may end up in here.
Ellipses (`…`) instead of `...`

Typography.
Ellipses in The Unknown
Check message log before posting message

Fixes #2111 "Closing the logbook creates a notification message for
finished objectives." _message_log contains previously displayed
messages so check that list before displaying.

Update to comments to match style per feedback from pull request.
Merge pull request #2115 from sabbott1877/scenario_duplicate_messages

fix #2111. Check message log before posting message
Merge pull request #2112 from unknown-horizons/ellipsis

Ellipses (`…`) instead of `...`