For range min and max, return the min or max (using ui.values) with the slider value in event handlers

[LaurentGoderre]

To allow generic handler to be applied to sliders it would be nice if range min and max sliders could include the min and max in the value (using ui.values). This would allow the handler to be completely independent and those value would not need to be retrieve somewhere else.

[Scott González]

Ask the widget what the min and max are.