Refactor to use objects for terrain/mod creation, added coin modifier

mario/mario_visitor.hpp

@@ -63,6 +63,14 @@ public:
         return newX;
     }
 
+    void setCoin() {
+        coin = true;
+    }
+
+    bool hasCoin() {
+        return coin;
+    }
+
 private:
     bool onGround = false;
     double groundY = 0;
@@ -77,6 +85,7 @@ private:
     SDLPP::Vec2D<double> rightleftpos;
     bool top_left_right = false;
     bool jumping;
+    bool coin = false;
     SDLPP::Vec2D<double> movement_blockage;
 };