MPI Infrastructure - Githubissues

The objective is to wrap and add MPI to the project and provide some basic infrastructure for multi-process computations. Broadly then:

Introduce MPI.
Wrap some operations for NeoFoam types.
Provide some basic parallel operations for fields (although probably not into the fields yet).
Some form of testing (@greole @MarcelKoch I think I will need some help for this).

exasim-project / NeoFOAM