- Implemented AS3GraphicsDataShapeExporter.beginBitmapFill()

- Added ImageDecoderAsync

Usage:
ImageDecoderAsync.decodeAsync(swf, function(imageDecoderAsync:ImageDecoderAsync):void {
   var exporter:AS3GraphicsDataShapeExporter = new AS3GraphicsDataShapeExporter(swf, imageDecoderAsync);
   shape.export(exporter);
})