Update Potassco Apps

[susuhahnml]

It is also hard to find, I am not sure if documentation is the best place.

[nrueh]

I agree, I think I have never seen this part before but it seems very relevant nowadays so maybe it should be on the front page even.
Also maybe it should be renamed to applications instead of apps?

[nrueh]

And I imagine this is where repos like the COOM Suite would go?

[rkaminsk]

We could also combine apps and labs.