Response files with ampersand

[davidgardenier]

Response files are occasionally being read in to XSPEC with an ampersand at the end of the file name. I thought I had fixed this earlier in the year, but still occasionally crops up. Perhaps the version of astropy/xspec have changed in the mean time, leading to different behaviour. The quick fix is to (manually) copy the response name (without including the ampersand) into the queried input on which XSPEC stops, and press enter. Means some additional oversight is needed for some objects (unsure when this issue does or doesn't pop up).