Achievements achieved

I finished the implementation of the achievements system and the main screen showing all the achievements in the game. There are still a few items to clean up like,

• Secret achievements are not implemented yet
• If you reach to achievements at the same time then you only see one of them
• You cannot clear achievements
• Achievements and high scores are stored separately

Nevertheless, the system works pretty well and the overall look and feel is quite nice. It definitely adds something to the game. Currently, I have only implemented this on QANAT but I plan to add this to Exogene also and to put it in any new games.