Correct inspector Delete Save

Now uses method in SaveManager directly to prevent duplicate and divergent path.
Fix #808

Assets/Fungus/Scripts/Components/SaveManager.cs

@@ -235,7 +235,7 @@ namespace Fungus
         /// <summary>
         /// Deletes a previously stored Save History from persistent storage.
         /// </summary>
-        public void Delete(string saveDataKey)
+        public static void Delete(string saveDataKey)
         {
 #if UNITY_WEBPLAYER || UNITY_WEBGL
             PlayerPrefs.DeleteKey(saveDataKey);

Assets/Fungus/Scripts/Editor/SaveMenuEditor.cs

@@ -19,7 +19,7 @@ namespace Fungus.EditorUtils
 
                 if (saveMenu != null)
                 {
-                    PlayerPrefs.DeleteKey(saveMenu.SaveDataKey);
+                    SaveManager.Delete(saveMenu.SaveDataKey);
                     FlowchartWindow.ShowNotification("Deleted Save Data");
                 }
             }