Improve links to Chandra images

[Doug Burke]

http://chandraobs-devel.herokuapp.com/obsid/15324 fails to show a Chandra image because it is an interleaved-mode observation and so needs "_e1" or "_e2" added to the file name - see http://cda.cfa.harvard.edu/chaser/startViewer.do?menuItem=image&obsid=15324