Parallel instances of polyMPO #76
Description
Some comments, TODOs and open questions:
1. Ensure when a polyMPO mesh is created it contains all the halo layer information too.
2. Ensure particles are initialized only in cells on processes where they are owned.
3. Confirm that when we get mesh fields from MPAS, these fields are defined not just on the "owned" cells/vertices but on all the cells/vertices (note this applies to mesh fields only).