Fix app for build 7 update; added UI support for adjusting grid size

- Build 7 update broke the controllers because I did not include the "android.hardware.vr.headtracking" uses-feature in the manifest. Because of this, the headset was incorrectly registered as an Oculus Go. Looks like they started to enforce this setting in the latest update.
- Added support for adjusting the grid size in the settings panel.

Assets/Scripts/Config.cs

@@ -22,7 +22,7 @@ namespace QuestAppLauncher
             public int cols = 3;
         }
 
-        public GridSize gridSize;
+        public GridSize gridSize = new GridSize();
     }
 
     /// <summary>
@@ -54,6 +54,10 @@ namespace QuestAppLauncher
                     Debug.Log(string.Format("Failed to read config: {0}", e.Message));
                 }
             }
+            else
+            {
+                Debug.Log("Did not find config file: " + configFilePath);
+            }
         }
 
         /// <summary>