Update OpenFOAM easyblock

- treat all MPI toolchains the same way
- Use EASYBUILDMPI instead of EASYBUILD as name MPI name as it has to contain 'MPI' to build MPI-based libraries
- Add sanity checks for dummy/libPstream.so and mpi/libPstream.so
Add sanity check for OpenFOAM
Merge branch 'develop' into openfoam_cleanup
Merge branch 'develop' of github.com:hpcugent/easybuild-easyblocks into openfoam_cleanup
Merge branch 'develop' of github.com:hpcugent/easybuild-easyblocks into openfoam_cleanup
make sure that expected subdir is there after extracting
move all files if they're not in expected directory after unpacking
move into install subdir
ignore error on adjusting permissions (e.g. broken symlinks)
fix sanity check w.r.t. OpenFOAM-Extend differences
Merge branch 'boegel-openfoam_cleanup' into openfoam_cleanup
Merge pull request #436 from besserox/openfoam_cleanup

OpenFOAM EasyBlock cleanup and update