GISAS with specular peak broken, and no test complains

Forthcoming MR will break computation of specular index - but no test complains.

added Core Example bug test labels

mentioned in commit 6dde8c7f

mentioned in merge request !2091 (merged)

mentioned in commit a43db543

mentioned in merge request !2093 (merged)

mentioned in commit f5f4d2b9

closed with merge request !2093 (merged)