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.

Also, let's take out the custom `elevation` code. The elevation really should be up to the user, not automatically picked. And it doesn't change based on the hover or active focus state.