Add Logo Variant with JSC next to FZJ

The CD allows for having a variant of the Jülich logo which has the institute's name next to it.

This merge

• adds an example logo for Jülich Supercomputing Centre (based on a logo from BSCW, which I cleaned up and added protection space for; and reduced the file size)
• adds a Beamer template to use this logo (footer element4 → jsc) (the raisebox{} is added to place it in alignment with "Slide", like the usual logo is)
• adds a slide for the tutorial showing how to use this logo and how to add another institute's logo