Added README.sh file, which is also executable to checkout the required

DUNE modules. Added additionalfiles subfolder containing
istlvectorbackend, which has to replace the original file as described
in the README.sh


git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@12506 2fb0f335-1f38-0410-981e-8018bf24f1b0