Match terminology with ReverseWay action
Rewrite d3.keybinding

A keybinding now represents a set of key commands that can
be unbound as a set. Multiple keybindings are possible, and,
providing a namespace is provided to the constructor, will
not conflict with each other.

Also, key combination strings such as ⌘+A are now supported.
Hook into undos in a different way

This way doesn't depend on details of keybindings and
the undo button.

Also, implement this in DrawArea mode.