we disable MPI by default as it might result in compilation issues
with newer compilers and the models do not work reliably anyway. also
the conditionals for building the handbook are refined and
summary status messages are added for LaTeX and the handbook.

git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@5033 2fb0f335-1f38-0410-981e-8018bf24f1b0