Static method to create a reader from a reader clazz.

        @param clazz:      the reader class name
        @param readername: the reader name

def createReader(clazz, readername):
        """Static method to create a reader from a reader clazz.

        @param clazz:      the reader class name
        @param readername: the reader name
        """
        if not clazz in ReaderFactory.factories:
            ReaderFactory.factories[clazz] = get_class(clazz).Factory()
        return ReaderFactory.factories[clazz].create(readername)