Notable items include the column show/hide buttons, which were
straightforward except for the "determine the default width" part,
and the font picker, which is no longer a standard dialog. The
latter was complicated by the absence of a good way to detect
whether a font is mono-spaced or not without calling back into code
meant for WinForms font manipulation (with a dash of PInvoke).
Yay WPF.
Also, enabled character ellipsis for code list items.
These just needed to have methods added to the command definitions.
Also, added a style to the toolbar buttons so they fade when not
enabled.
Also, fixed the DataFileLoadIssue dialog, which was seriously broken.
