Display slogans on section pages too

[pbelmans]

This will be tricky though, given the way we display things...

[aisejohan]

You can ask for the same thing with references and historical remarks. I am not sure how one would do this? But maybe we can do the thing suggested in #77 also for the "Lemma 1.2.3" links and moreover have the s, r, and h be targets where if you hover your mouse over it, then the slogan, reference, or historical comments can be viewed in a little window (as on wikipedia pages when you hover over a citation thingy (see for example the very sad http://en.wikipedia.org/wiki/2014_West_Africa_Ebola_virus_outbreak).