ActiveQt: Add support for "Implemented Categories"

ActiveX provides a mechanism for tagging components with a list of "Implemented Categories". These categories are useful for querying the registry for a subset of all available ActiveX components, based on capabilities/categories.

It would be great if QAxClass could be extended with ability to parse and register "Implemented Categories", based on Q_CLASSINFO metadata without having to subclass QAxFactory as mentioned in http://doc.qt.io/qt-5/qaxfactory.html#registerClass .

Reference: https://msdn.microsoft.com/enus/library/windows/desktop/ms682451.aspx