Give the user a message when a merge task JSON contains "coordinate-status" : "misplaced"

[hubbardp]

In this case, the suggested merge position, and thus the grayscale viewer, could be arbitrarily far from where the bodies actually would merge (if they merge).

Note that in /groups/flyem/data/hemi_brain/whole_hemi_brain/focused-sessions, this case occurs 8700 times out of 230303 "adjusted" case (3.8% of those cases).