assigning or reassiging position sets both histfig1 and histfig2 to the assignee's histfig id unassigning position sets only histfig1 to -1, histfig2 untouched
see https://github.com/jjyg/df-ai/blob/master/ai/population.rb#L627-L640
assigning or reassiging position sets both histfig1 and histfig2 to the assignee's histfig id unassigning position sets only histfig1 to -1, histfig2 untouched
see https://github.com/jjyg/df-ai/blob/master/ai/population.rb#L627-L640