Use Qt Controls as the base for Button

I am not sure what the opinion of QtQuick.Controls is in this project, but there are some features we get from them for desktop experience, and integration with things like input methods and accessibility.  There is an issue here with the Theme though because it may need its own color to operate correctly.  If there is no problem with controls I would want to move Action to use them so they can integrate into the Button object eaiser.

Can you take out the "white" definition and instead alias the `button.backgroundColor` to the style `backgroundColor`? That is because the button is transparent when the elevation is 0 and white when the elevation > 0.