Enable message passing of a photon struct with MPI

[EdHone]

In order to scale the capability of the model beyond a single process node, MPI needs to be integrated into the infrastructure of the model. The base form of this is enabling the Photon struct to be passed from process to process using MPI.

[EdHone]

Development branch created: photon-buffer

[EdHone]

PR created #51

[EdHone]

Code snippet for managing environment variables with Spack:

from spack import *

class AetherusEnv(BundlePackage):

    version("test")

    depends_on("hdf5")
    depends_on("netcdf-c")

    def setup_run_environment(self, env):
        env.set("HDF5_DIR", f"{self.spec['hdf5'].prefix}")