refine the structure
refine the toXtext() method
Chart.toXtext() results in the order defined in openHAB wiki
[DEBUG] Util.toXtext()
rename some local variables
Colorpicker.xtext() unit test DONE
Frame.xtext() unit test DONE
Group.xtext() unit test DONE
Image.xtext() unit test DONE
List.xtext() unit test DONE
Selection.xtext() unit test DONE
Setpoint.xtext() unit test DONE
after some modification to Util, Slider.toXtext() has passed the unit test