#256 Peak at m/z=0 not handled right

[Dave Musicant]

Occasionally with ATOFMS data a peak appears at m/z=0. This appears in the peak list in Analyze Particle, but doesn't appear in the graphs. It should appear in one of the graphs, or it shouldn't be there at all. Which should it be?

If m/z=0 is to be removed, add a unit test to make sure that it happens. If m/z=0 is to be kept, add a unit test to make sure that it appears in the list of peaks that are being plotted.

To duplicate the bug: it happens in the St. Louis dataset for atomids 660, 662, 663, and 664.