Undo the last change I made

Puts back what an earlier call changed: {"token": "..."}, the undo.body of that call's response. Works for 24 hours. When the same slide, slideshow, schedule or screen was changed again since, answers NeedsClarification with a choice that overwrites that later change (force: true); ask the person before sending it. Returns { "restored": n }. Not covered: pushed live data, slideshow deletion, screen settings, and which TV was bound before a re-pairing.