Split IndexRearrangement into two classes

...tructureInitializer/GridReaderGenerator/GridGenerator.cpp

...aStructureInitializer/GridReaderGenerator/GridGenerator.h

...izer/GridReaderGenerator/IndexRearrangementForStreams.cpp

...alizer/GridReaderGenerator/IndexRearrangementForStreams.h

.../GridReaderGenerator/IndexRearrangementForStreamsTest.cpp

...tializer/GridReaderGenerator/InterpolationCellGrouper.cpp

...nitializer/GridReaderGenerator/InterpolationCellGrouper.h

...izer/GridReaderGenerator/InterpolationCellGrouperTest.cpp