Removed boost::array dependency in mpi::BufferDataTypeExtensions (was already partly done as part on #59)

Michael Kuron authored 7 years ago and Christian Godenschwager committed 7 years ago

API changes in blockforest::PhantomBlockForest, blockforest::loadbalancing, pe::amr::weight_assignment
mpi can now only send/receive walberla::optional instead of boost::optional

Also remove some unneeded boost includes

If you have access to the old closed source waLBerla repository, you may restore the complete history with the following command
git fetch git@i10git.cs.fau.de:software/walberla.git 'refs/replace/*:refs/replace/*'