The invention is described with reference to the drawings. The section “Description of the Drawings” consists of two parts, namely a “Brief Description of the Drawings” and a “Detailed Description of Exemplary Embodiments”. In the “Brief Description of the Drawings,” each drawing is explained in a single sentence, indicating what is depicted in the respective drawing. In the section “Detailed Description of Exemplary Embodiments,” embodiments of the invention are explained in detail.