- Add keyboard acelearators for non-navigation keys
- Use a switch statement on the key code for the rest.
The intention was to make the keyboard navigation clearer. My original
idea way to make everything a keyboard acelerator, but this got clumsy,
requiring four shortcuts for some navigation to cover combinations
of using the numpad, and with the Ctrl key. I also ran into some
problems on GTK because the Shift+WXK_NUMPAD_* events don't work
as acelerators, but it seems they also don't work in OnKeyDown.
