Ported the column width stuff from EditAppSettings, which it turns
out can be simplified slightly.
Moved the clipboard copy code out into its own class.
Disabled "File > Print", which has never done anything and isn't
likely to do anything in the near future.
Also, added a note to 2019-local-variables about a test case it
should probably have.
After thrashing around a bit, I had to choose between making the
uniquifier more complicated, or making de-duplication a separate
step. Since I don't really expect duplicates to be a thing, I went
with the latter.
Updated the regression test.
This hits most of the edge cases, but doesn't exercise the two
duplicate name situations (var name same as user label, var name
same as project/platform symbol).
Also, fixed a bug in the EditDefSymbol uniqueness check where it
was comparing a symbol to itself.
