Filtering by languages, minor improvements

The output is now in alphabetical order, so it's a lot easier to find the game you want in the list 😄
Same thing for the logs: it's all now in alphabetical order

And a new feature, --only-selected-langs, because the current --languages option was not a filter! 😨
Yes, I never realized it would be unclear to users that the --languages option was merely a prioritization mechanism, not a hard filter. Well, now I mention that peculiarity in the README.

Since changing how --languages works would be a major change, I decided to introduce the new option so people who want to filter by the languages can do so 😎