Sliders and scroll bars should scale to stepSize

[imagejan]

When using non-integer numeric inputs with style="slider" or style="scroll bar", the UI widgets only support integer steps (because the underlying JSlider and JScrollbar objects only support int values).

This can be improved by scaling the slider range to the [min; max] range as follows:

• slider.setMinimum(0)
• slider.setMaximum( (max-min) / stepSize )
• slider.setValue( (value-min) / stepSize )
• value = slider.getValue() * stepSize + min

and setting the slider/scrollbar labels to string representations of the scaled values.

[ctrueden]

Resolved by #35.