Issue title: Preferred to use RectTexture
 Issue body: Texture.empty

var isPot:Boolean  = (origWidth == potWidth && origHeight == potHeight);
            var useRectTexture:Boolean = !mipMapping &&
                Starling.current.profile != "baselineConstrained" &&
                "createRectangleTexture" in context && format.indexOf("compressed") == -1;

 Comments: 
 Comment 0: var useRectTexture:Boolean = *****

remove !isPot

 Comment 1: Duplicate of #409 

In short: this will be implemented soon!

{'source': 'GithubIssues', 'repo_name_with_owner': 'Gamua/Starling-Framework', 'issue_id': 24162801, 'repo_stars': 2562.0}