Generating a world with easier settings disables achievement

[mophydeen]

Note: I have all achievements so I don't know when a game is valid for achievements or not.


- show the player during generation that this map will not be eligible for achievements.
* red "generate" button
* specific red dropdown at the cause (when enabling pieceful mode make the title and checkbox red)

- Please also add ingame an option to see if the game is valid for achievements or not:
* add a /command
* text or red color in achievements frame