[Dune] dune.module and the module names

[Christian Engwer]

Hi,

for some time it was necessary that the dune names were specified as
something like
dune_istl
and for the configure script you had to supply
--with-duneistl

All this was not very intuitive and some of you legitimate requested
that I should change this.

>From now on, configure support this feature and I also switched all
the major modules to a unique naming convention.

So please be warned :-) you will have to update the dependencies of
your modules.

Cheers Christian