Robustness if user provides non contiguous input partitions

[Algiane]

Test if we support non-contiguous input partitions. I think that Metis doesn't but I don't know for Scotch or advancing-front interface migration. I either don't know if we fix contiguity before first repartitionning.

• Creation of a continuous integration test case
• Check if we fix contiguity before first partitionning
• If not check if Metis is robust to this
• if Scotch is
• if advancing-front method is