loadSources(sourcesArray, texturesOptions = {}, successCallback, errorCallback) {
        for(let i = 0; i < sourcesArray.length; i++) {
            this.loadSource(sourcesArray[i], texturesOptions, successCallback, errorCallback);
        }
    }
This method handles the sources loading process

     params :
     @sourcesArray (array): array of html images, videos or canvases elements
     @texturesOptions (object, optional) : Parameters to apply to those textures (see Texture class). Will be merged with the mesh default textures options
     @successCallback (function): callback to execute on source loading success
     @errorCallback (function): callback to execute on source loading error
*