Widget factory: Make the methods enable() and disable() act via _setOpti...

...ons() instead of _setOption().

If a subclass chooses to implement all its option handling (including "disabled") in the _setOptions() method, then currently it will also have to separately implement _setOption() solely for the purpose of the "disabled" option, because the enable()/disable() methods in the factory do not funnel the option handling through _setOptions().

Notice that with this change if said subclass chooses to chain up during _setOptions() to benefit from the code in the factory's implementation of _setOption() it could still do that, because the factory's implementation of _setOptions() calls _setOption() for each option set, including "disabled".