re-added grid-rendering to the editor

rebuild grid/navMesh 3D data only if needed

mapview/3D/grid/GridModel.h

@@ -26,6 +26,8 @@ private:
 	Grid<MyNode> grid;
 	Floorplan::IndoorMap* im;
 
+	int buildID = 0;
+
 public:
 
 	GridModel() : grid(gridSize_cm) {
@@ -78,6 +80,10 @@ public:
 
 	};
 
+	int getBuildID() const {
+		return buildID;
+	}
+
 	void rebuild(Floorplan::IndoorMap* im) {
 
 		Listener l;
@@ -88,6 +94,8 @@ public:
 		Importance::addImportance(grid, &l);
 		//Importance::addImportance(grid, 400);
 
+		buildID = rand();
+
 	}
 
 };