List the Kwant features that are highlighted in each tutorial text
I was explaining to someone how value functions in Kwant work, and wanted to refer him to the tutorial. it was not immediately clear to me which tutorial first covers value functions. By grepping the tutorial scripts for "args" I found out that it's the chapter "More interesting systems: spin, potential, shape". I think it's good to have such physical titles, but we should also clearly list which Kwant features are highlighted. This information is actually present, but it's hidden in the example scripts themselves. I think that it should be moved into the tutorials. We could show it after the section titles.