make popups more predictable

Related to https://github.com/ArcBees/GWTP/issues/554
There's a check for isVisible() in onReset now so if a popup is not visible it won't be called and onReset won't propogate to children on hidden presenters so I don't think it will effect performance.

But I was wondering if that's correct do you call onReset for non visible presenters at the moment?