It felt a little weird tying it to the asm generation setting,
so now it's just another checkbox in the export options.
Implemented the feature for plain text output. Did some rearranging
in the code. Fixed suppression of Notes in text and CSV.
Also, removed "include symbol table" from export dialog. You can
exclude the table by removing it from the template, which right
now you'd need to do anyway to get rid of the H2 header and other
framing. To make this work correctly as an option we'd need to
parse the "div" in the template file and strip the whole section,
or split the template into multiple parts that get included as
needed. Not worth doing the work until we're sure it matters.
This feature "exports" the source code in the same format it appears
in on screen. The five columns on the left are optional, the four
on the right can be resized. Exported text can span the entire file
or just the current selection. Output can be plain text or CSV.
(I still haven't figured out a good use for CSV.)
The old copy-to-clipboard function is now implemented via the export
mechanism.
This adds a new clipboard mode that includes all columns. Potentially
useful for filing bug reports against SourceGen.
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.
