LoadingManager for texture

[Dalas]

This feature adds availability to control process of textures uploading in only one LoadingManager.

let manager = new THREE.LoadingManager();
manager.onProgress = function (url, itemsLoaded, itemsTotal ) {
    console.log( 'Started loading file: ' + url + '.\nLoaded ' + itemsLoaded + ' of ' + itemsTotal + ' files.' );
};
manager.onLoad = function ( url, itemsLoaded, itemsTotal ) {
    console.log( 'Finish loading' );
};
this.loadingManager = manager;

........

<texture url="/texture1.png" loadingManager={ this.loadingManager } />
<texture url="/texture2.png" loadingManager={ this.loadingManager } />
<texture url="/texture3.png" loadingManager={ this.loadingManager } />

Console output:

Started loading file: /static/images/planets/texture1.png.
Loaded 1 of 3 files.
Started loading file: /static/images/planets/texture2.png.
Loaded 2 of 3 files.
Started loading file: /static/images/planets/texture3.png.
Loaded 3 of 3 files.
Finish loading