Prevent spam submissions to Census

[rufuspollock]

Census form does not have any guard against spammers and with increasing visibility we've started to see issues.

Several ways to address this:

• Start requiring proper login to submit
• Recaptcha or similar - Add captcha on Census submissions form #247
• Simple hack option - e.g. ensure that JS is on and working (e.g. use JS to create a button to add a field to the form)

[mattfullerton]

I was intending to add a recaptcha - but login might be more elegant. Does #261 mean you're for a login? In which case we can close this. Let's not forget to undo ac766ff (hiding submitters' names) when we're done.

[rufuspollock]

FIXED. Now that #261 (login) is done this should be fixed.