"-dilation-gauss" and "-erosion-gauss" should be working now

Bug fix. The dilation and erosion filters have been working correctly for over a week. But the command-line arguments "-dilation-gauss" and "-erosion-gauss" were not being parsed correctly, so the correct code was not being invoked. (And last week, when I tested it, I misspelled the names of these arguments, so I did not notice the problem. Amazingly, the two errors cancelled out.) Hopefully these filters are working and are behaving consistently with the documentation now.