Meshes in statepoint files vs inputs

[pshriwise]

One interesting thing to note is that to visualize tally data on a mesh in the plotter the mesh in the input XMLs must be the same as the mesh in the statepoint file. Meshes can be added to an initialized model, however and it might be interesting in the future to add meshes to the initialized OpenMC model (in openmc.lib) based on the mesh specifications in the statepoint file.