ColorPicker improvements
- Remove width == 0 check, behavior has changed in UIElement
  (see: f5a5c12a03dcd6da84967dddba602dcf7e9d4d34).
- Use raw BitmapData assigned in Style.css
- Scale positions in spectrum pixel calculations
- Mouse handling: drag & release outside.
Fix stack-overflow in DataButton change signalling
Fix nullpointer