Took another swing at doing things WPF-style. Ended up with TextBox
objects backed by integer fields, which worked pretty well but
didn't get the min/max values. Set up validation instead, once I
figured out how to make it update in real time.
Relatively straightforward, thanks to the way WPF ComboBoxes work.
Spent some time fiddling with the column width text boxes, but
ended up with essentially the WinForms approach.
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.
