- Renamed applications to utils.
- Added utils/ProcessMPI.h (based on BlockProcessor_MPI.h from Cubism-MPCF).
- Added CubismMPI class in pywrapper/Cubism/__init__.py
- Added advection_MPI example.

Changes to source/:
- Commented out an include for vectorization (not used within Cubism).
- Added some parentheses to silent the -Wextra warnings.
- Added virtual to a ~SynchronizerMPI.