Draw2D touch version 5.8.0 released

+ implement zoom as new CanvasEditPolicy
+ new zoom implementation with MouseWheel support
+ fixing background gradient error if transparency is set to <1 for ports
+ fix broken MySlider implementation in the samples
+ don't force redraw or call of "attr" if the attributes are empty
+ remove deprecated currentHoverElement variable in ports

Mouse Wheel Zoom: New for this release is a mouse wheel zoom. This tool requires you to press the [Shift] key to activate the mouse wheel zoom function. Holding [Shift] and rolling the mouse wheel forward zooms in, while rolling it backwards zooms out. Draw2D will shift the center of the zoom focus to where your cursor is on the screen, allowing you to zoom in and out from one area of a presentation to another smoothly.