Restart files should only contain necessary fields

[bigfooted]

Restart files currently contain fields that are not necessary for restarts, like residual information, pressure coefficient, etc. I propose to store only the fields that are necessary for restarts in the restart file. This will keep the size of the restart files to a minimum.

I think we only need to store the transported variables, or do we need to store more information for perfect restarts, or adjoints?