Update Game to Godot 3

I have update Caduceus to Godot 3. It's been a long, long, long time since I updated the game, but it's now time! I do want to try to make more QoL to this game to be much more presentable, and playable. I want to give the player more options to the game. I will learn more about how to use Godot, and make it easier to play. Let me know what you think. Comment about it!