Separate form from view labels

[wfdd]

When viewing a candidate, we don't need to be given an example of a Twitter username; that only serves to confuse. Similarly, for extra fields, I might wanna provide some guidance for contributors in the label, but there's no reason for that to be visible when not editing a candidate.

Alternatively, we could create a new field for usage instructions and normalise the labels of gender, dob, etc.

[wfdd]

It looks like Django's actually got a 'help_text' field which I hadn't noticed.