Merge remote-tracking branch 'origin/feature/9440_stitch1d_many'
Merge remote-tracking branch 'origin/feature/8562_flag_missing_source_file_before_reduction'
Refs #9564. Reversed direction of POLDI data.

Unit tests had to be adjusted because of element ordering. While looking at the file,
made some performance improvements.
Merge branch 'feature/9564_reverse_reading_order_poldi_data' into develop