Move files to the ui/ folder

src/core/session.ts

 import { Viewport } from './viewport';
 import { Settings } from './settings';
 import { Stats } from './stats';
-import { StatsPanel } from './stats-panel';
+import { StatsPanel } from '../ui/stats-panel';
+import { Gizmos } from '../ui/gizmos';
 import { Frame } from './frame';
 import { Tracker } from '../trackers/tracker';
 import { Time } from './time';
-import { Gizmos } from './gizmos';
 import { Source } from '../sources/source';
 import { asap } from '../utils/asap';
 

src/core/viewport.ts

 import { Nullable } from '../utils/utils';
 import { Resolution } from '../utils/resolution';
 import { Utils } from '../utils/utils';
-import { IllegalArgumentError, IllegalOperationError, NotSupportedError, AccessDeniedError } from '../utils/errors';
 import { HUD, HUDContainer } from './hud';
 import { AREvent, AREventTarget, AREventListener } from '../utils/ar-events';
+import { IllegalArgumentError, IllegalOperationError, NotSupportedError, AccessDeniedError } from '../utils/errors';
 
 
 
     /** The canvases of the viewport */
     private readonly _canvases: ViewportCanvases;
 
-    /** Fullscreen utilities */
-    private readonly _fullscreen: ViewportFullscreenHelper;
-
     /** Resize helper */
     private readonly _resizer: ViewportResizer;
 
     /** The current size of the underlying SpeedyMedia */
     private _mediaSize: ViewportSizeGetter;
 
+    /** Fullscreen utilities */
+    private readonly _fullscreen: ViewportFullscreenHelper;
+
 
 
 
         this._hud = new HUD(this._subContainer, settings.hudContainer);
         this._canvases = new ViewportCanvases(this._subContainer, initialSize, settings.canvas);
 
-        this._fullscreen = new ViewportFullscreenHelper(this.container);
         this._resizer = new ViewportResizer(this);
         this._resizer.setStrategyByName(this._style);
+
+        this._fullscreen = new ViewportFullscreenHelper(this.container);
     }
 
     /**

src/core/gizmos.ts → src/ui/gizmos.ts

 import { Resolution } from '../utils/resolution';
 import { Nullable, Utils } from '../utils/utils';
 import { IllegalArgumentError, IllegalOperationError, TrackingError } from '../utils/errors';
-import { Viewport } from './viewport';
+import { Viewport } from '../core/viewport';
 import { Tracker } from '../trackers/tracker';
 import { ImageTrackerOutput } from '../trackers/image-tracker/image-tracker';
 

src/core/stats-panel.ts → src/ui/stats-panel.ts

  */
 
 import { SpeedySize } from 'speedy-vision/types/core/speedy-size';
-import { Settings, PowerPreference } from './settings';
-import { Viewport } from './viewport';
+import { Settings, PowerPreference } from '../core/settings';
+import { Viewport } from '../core/viewport';
 import { Tracker } from '../trackers/tracker';
 import { Source } from '../sources/source';
 import { Utils, Nullable } from '../utils/utils';
 
     /**
      * Constructor
-     * @param parent parent element of the panel
+     * @param viewport Viewport
      */
     constructor(viewport: Viewport)
     {