store summary statistics for users

[goastler]

No description provided.

[goastler]

@HughParry said about this in one of our meetings. Essentially if we store the # of correct and incorrect captchas, we can use it as a summary statistic going forwards. The only issue is when these numbers get high (e.g. hundreds / thousands) it would take many captchas to move the summary statistic at all, so we may want to put a limit on this of sorts