Primary navigation sidebar should optionally collapse

[aaroncox]

Desktop users currently have a navigation always displayed on the left side of the screen. These users should be able to collapse/hide that menu in some way. The contents of the content panel should be able to expand and fill that new space if needed, but retain a maximum width.

Not sure whether it should just be hidden, or if it should turn into a minimal sidebar with icons - including an icon that lets it expand again.