Update inputs improved

[werpuc]

There should be a solution for nice handling errors in input updates (e.q. updateSliderInput()), as validate() is not suitable.

If the object update*Input() uses is not ready yet, or has working validate, there is an error. Validate() message cannot be propagated - it is an update, not an object. Currently, I'm solving this situation with additional if conditions (similar to existing validates), but I hope it is a temporary solution.