Partition balancer
vtkPartitionedDataSetCollection (PDC) and vtkParitionedDataSet (PD) do not require that all ranks have some number of paritions. However, I am sure we'll encounter old filters that do not handle this correctly and we may need to provide a temporary workaround till those filters are fixed to avoid deadlocks. To address this, lets create a new filter that simply ensures all ranks have same number of partitions for the input PDC or PD.