implement captcha+solution

(Theres's a note on implement modules that says to do this as a module.)

Captcha cardtype - name is challenge, content is response

If "|cardtype|+Captcha" (Toggle) exists and is 1, when Anonymous tries to edit/rename/cardtype change/delete/comment on cards of that type, then make there a captcha.

In English:

"Basic+*captcha" exists but is 0 (and is 'inherited' by other cardtype)

"Account Request+*captcha" exists and is 1

The Captcha card itself lists cards with "*captcha" as their right part in close view.