Add API for adding questions

- New route (send_selection)
- send_selection maps to a new view which adds a new question, using
data from the POST request.
Add more submission options

- Add ability to submit as any user sent in data
- Add ability to add tags
- Add ability to add more information in body
Small changes

- Ensure submitting as nonexistant user doesn't break things.
- Add beginnings of new models (claim/page)