Unify value from noUiSlider

[lionel-bijaoui]

There is a few problem with noUiSlider:

• It can't dynamically add or remove an handle. It can't wait for the value from the model to know if this is a double handle or not. So we need an option to explicitly tell if this is double or not (like with rangeSlider). EDIT: done in rename dateTime to dateTimePicker and slider to rangeSlider #72
• When using a single handle, noUiSlider format the data like this [Number, null]. It expect us to use slider.noUiSlider.get(). So, much like with date input, we need a formatValueToField and formatValueToModel to properly format data back and forth.

I'm on both issue and I will do a PR in the next days.

[icebob]

Nice observation. Thank you

[lionel-bijaoui]

Progress: I'm done with noUiSlider, I added some dynamic CSS class and CSS fix with scale.
There is something I can't do though: if you modify the same model with noUiSlider and rangeSlider, modification of rangeSlider make noUiSlider change too, but not the contrary.
I tried different solutions ( almost lost my mind) and was not able to avoid infinite loops. I don't know why, and I give up, since there is no real reason to use both sliders.

[lionel-bijaoui]

@icebob #73 is ready