Draw2D touch version 4.8.0 released

+ new composite figure "draw2d.shape.composite.Group"
+ new command CommandGroup to group a list of figures
+ new command CommandUngroup to group a list of figures
+ enhance the JSON Reader/Write for group support
+ new example composite_group which demonstrates the group feature
+ new EditPolicy for the canvas with extended keyboard handling and group/ungroup support "draw2d.policy.canvas.ExtendedKeyboardPolicy"
+ new method Canvas.destroy to free all resources and unbind all event handler
+ fixing missing parameter shiftKey/ctrlKey in Figure.onDrop
+ new method Figure.onCatch. This event is fired if an figure is dropped onto another figure.
+ it is now possible to hand over a draw2d.util.ArrayList to the Canvas.setCurrentSelection method
for multiple figures selection
+ fixing bug in Canvas.setCurrentSelection if multiple objects are selected before. Not all figures are unselected.