Major clean up and reorganization

- Upgraded to Godot 4
- Just remembered the basic principles are based on a tile editor, and dramatically simplified from there. Derp.
- New state machine and license display add-ons.
- Re-licensed under the GPL because Micropolis' assets aren't under a separate one.

json/zones/tower_names.json

@@ -1,5 +1,5 @@
 {
-    "tower_names": [
-        {}
-    ]
-}
+	"tower_names": [
+		{}
+	]
+}