Possibly fix issues finding icon locations in the rc file

The code for determining what to use for the rc file group name for each icon is a little confusing. There's the icon identifier, and the icon label. At some point using the icon identifier was preferred over the label, but I think in some cases one of those two might get written to the file, while the other ends up being used to read it back.

Frankly, I wish this had been done in a way where we just migrate old data to the new method, and then mark the rc file as having been migrated, but hopefully this will give us the best chance of at least reading something out of the rc file.

Closes #35 (closed).