#75 better keybindings editor wanted

[Oswald Buddenhagen]

the key bindings dialog is very unintuitive.
the first thing is, that it should be listed by function, not
by binding - yes, i know the implications ;).
then, nesting that many dialogs is plainly weird - it's sort
of a wizard. not that a wizard would be bad, but then
make it a real wizard with all dialogs at one hierarchy
level, with "next" and "back" buttons and make each
dialog preserve it's settings even when going back.