Merge pull request #4798 from RosettaCommons/roccomoretti/index_selector_reverse_message
Add warning message regarding the Index selector's reverse option.
Potentially counter-intuitively, the reverse option of the Index selector doesn't invert the selection, but instead invokes a count-from-end behavior.
Attempt to catch instances where users misuse this option, and print appropriate warning messages. (Particularly in cases with PDB numbering, where the count-from-end behavior doesn't really make sense).