Union QtWidgets Output Plugin

The Union QtWidgets Output plugin implements a QStyle for QtWidgets, which uses data from Union's intermediate layer to style QtWidgets. If there is no matching QStyleOption or QWidget declared for the element by the application, it will fall back to QCommonStyle.

Do note that QtWidgets Output has some limitations: Applications tend to expect very specific behavior from QtWidgets styles, so these limitations are there to preserve backwards compatibility.

Current limitations are: - layout-alignment, text-alignment and icon-alignment may not work properly in all elements. - ItemViewItem element follows the QCommonStyle size with padding applied. - ItemViewItem element does not support layouting, as QtWidgets applications declare the layouting on their own.