File communication in parallel for OpenFOAM

[nicolasdlss]

To tell OpenFOAM to perform an action such as save, a file save.coco is created.
This file should be read by all processes. When the last one has finished, a file save_ready.coco is written to tell CoCoNuT OpenFOAM has performed the action and the file save.coco is removed.
Currently, the file save_ready.coco is sent when the first process is ready. This can lead to problems when, e.g., the file save.coco is removed before all processes have seen it.
The creation of the file save_ready.coco and the removal of the file save.coco should only occur when all processes have finished the task.