Refactor the vtkRedistributeDataSetFilter for more modularity

The vtkRedistributeDataSetFilter now utilises a strategy pattern vtkPartitioningStrategy for encapsulating the partitioning algorithm to use when redistributing a data set. You can now change the partitioning strategy dynamically at runtime.

The previous strategy hardcoded into the vtkRedistributeDataSetFilter has been refactored into the vtkNativePartitioningStrategy class (inheriting from vtkPartitioningStrategy). No novel strategies are included in this development.

WARNING: The method vtkRedistributeDataSetFilter::SplitDataSet has changed signature and been made private. It no longer made any sense in the generic implementation proposed in this development.