Implement polls to be attached to reviews and forum topics.

Requirements:
- A button "add poll" adds the poll question and first answer (in javascript if enabled, with reloading if not)
- A button to add additional Poll questions (max number configurable) automatically
- Only registered users can vote. Voting in AJAX (if JavaScript enabled)
- A 'show results' button (in JS if enabled) to switch between results and the poll
- Permissions: anyone can add polls (at least for now)