Added the ability to reverse a ChunkedList to support some experimental work not included with this commit. Also beefed-up the unit test to ensure that the Contiguous and Slice representations for Chunk were being properly tested after performing a fault-injection exercise whilst testing the reversal functionality.
Fix for another edge case causing lots of degenerate one-item run lengths to be created without being fused together - this was killing performance for 'TestMergingOfVectorsInWithPartialTestVectors'.