Merged revisions r6654 to r6721 from trunk to sync the branch.

doc/buildsystem/buildsystem.tex

dune/common/densematrix.hh

dune/common/densevector.hh

dune/common/fvector.hh

dune/common/geometrytype.hh

dune/common/mpicollectivecommunication.hh

dune/common/parallel/test/syncertest.cc

dune/common/parametertreeparser.hh

dune/common/test/.gitignore

dune/common/test/Makefile.am

dune/common/test/deprtuplestest.cc

dune/common/test/fmatrixtest.cc

dune/common/test/tuplestest.cc

dune/common/tuples.hh

dune/common/tupleutility.hh

m4/dune_mpi.m4