Add hotkey for "Minimize Ribbon" button

[ks2_wmb]

I want a hotkey for this little guy.

The hotkey should perform whatever the user-selected behavior is for the GUI button.  Either it should minimize to your chosen state (tabs, panel titles, panel buttons), or it should cycle through all options.

I'm okay if this hotkey isn't assigned by default, but maybe assigning it by default isn't horrible?  Personally, I myself would assign this hotkey to my F11 button, to match the "fullscreen" hotkey in other applications (web browsers especially).