cluster configurations in cluster MPI

[abuts]

Cluster MPI starts MPIexec to run parallel jobs but currently works locally. To run on small MPI/Beowoolf clusters, one needs to provide appropriate cluster configuration to mpiexec (different parameters for linux, windows and probably mac). These configurations should be presumably located in herbert_core/admin/mpi_cluster_configs/ and user should be able to select from them. Some test configs are there but they are not tested and not provided to mpiexec.

As the result of this ticket, users should be able to add cluster configurations, select from them and mpiexec run on various clusters.

I was creating test clusters using oracle VM