Integrate algorithm for multi-MPI-ranks

gatherRequiredHaloMesh() needs to be modified

Two options:

• Option "sequential shared clusters"
• Option "parallel shared clusters"

Open tasks:

• Discuss halo mesh communication, connection to queue (@pgupta, @brgerhar, @webmanue, @ssaxena, @mspinola)
• Dicuss remaining issues (@brgerhar, @webmanue, @pgupta, @ssaxena, @mspinola)
• Add documentation for halo mesh exchange