Make gridSize in Services pass correct signature

Both need to conform to Point<int> to be accepted by the engine.

lib/service/configuration_service.dart

@@ -37,7 +37,7 @@ class ConfigurationService {
   }
 
   void setGridSize({int x, int y}) {
-    _sim.gridSize = Point(x ?? gridSize.x, y ?? gridSize.y);
+    _sim.gridSize = Point<int>(x ?? gridSize.x, y ?? gridSize.y);
   }
 
   Point<int> get gridSize => _sim.gridSize;

lib/service/simulation_service.dart

@@ -19,7 +19,7 @@ class SimulationService {
     _engine.clear();
   }
 
-  void set gridSize(Point size) {
+  void set gridSize(Point<int> size) {
     _engine.engine.gridSize = size;
   }