Editor layout

- Cleanup the editors a bit
- Editor foldout scope
- Cell size to editor (this is user preference data, could be put in EditorPrefs later)

Runtime/SceneGrid.cs

@@ -5,15 +5,12 @@ namespace VertexColor.ScenePartition
     [System.Serializable]
     public class SceneGrid
     {
-        [SerializeField]
-        public int cellSize = 10;
-
         [SerializeField]
         private SceneGridDictionary grid = new SceneGridDictionary();
 
         public SceneGridDictionary Grid => grid;
 
-        public void Insert(ulong scenePartitionId, Vector3 point)
+        public void Insert(ulong scenePartitionId, Vector3 point, int cellSize)
         {
             int gridId = CalculateGridPosition(point, cellSize);
             if (grid.TryGetValue(gridId, out GridList ids))