[WIP] RangeSlider

[ ] Base class is now __Slider__
[ ] Changed __RangeStart__ to __Minimum__
[ ] Changed __RangeStop__ to __Maximum__
[ ] __Minimum__ cannot be set greather than __RangeSliderStart__ and vice versa.
[ ] __Maximum__ cannot be set smaller than __RangeSliderStop__ and vice versa.
[ ] The difference between __Minimum__ and __Maximum__ cannot be smaller than __MinRange__