This PR changes the way the halo size is set.
Now it is possible to set the halo size only if the patch is all on a single process.
The function _getMaxHaloSize is overridden also for volunstructured, in this way it is possible to set more the one layer of ghost also for this patch.
I moved the changes that allows to set the halo layer on already partitioned patches in #310. This pull request is now only about enabling multiple halo layers on unstructured patches.
This PR changes the way the halo size is set. Now it is possible to set the halo size only if the patch is all on a single process. The function _getMaxHaloSize is overridden also for volunstructured, in this way it is possible to set more the one layer of ghost also for this patch.