[Dune] Update of the official Homepage / dunedesign.png

[Christian Engwer]

I kind of agree with Andreas.

> I like them, but I prefer version B.  Although it is more cluttered, it does
> inlcude extra grid modules, and I think it is important to show that this is
> supported.

In general I prefer design over completeness. I prefer the simplicity
of A and would also prefer to have the application visually separated,
like in my original diagram. I might be less accurate (but this mainly
depends on the interpretation), but looks more appealing.

> Also, I would say "third party library modules" instead of "third party core
> modules".  Similar, I don't like the "core" in "core discretization modules",
> though I must confess I don't have a better idea.

I think it is sufficient to say "discretization modules". It is still
possible to use other discretization modules, but these are the ones
suggested by the dune developers; which ones we include here is a
second question.

Christian