Add "wide-sub" window to three+

- Make "sub" visible by default.
- Move "sub" to the side bar.
- Add "wide-sub" to the place where "sub" were before.  Use it only
  when the buffer to be shown requires wide window.
Add ne2wm:dp-three+-toggle-wide-sub
Add ne2wm:require-wide-window-p
Add ne2wm-plugin-vcs.el