implement captcha+todo

these two maybe handling by *not* having captcha on by default?

• √ don't always put recaptcha js tags in header?-- make this load-on-demand yaay!
• PENDING (deploy to pinz) make decision about recaptcha key/  make it optional  (currently explodes without key in wagn.rb)

• rollback?
• √handle signup  (make signup into card creation?)
• √migrate *captcha = 'on'   by default?
• √fix delete
• X "deny all" url for account requests (if easy) --> moved to own ticket.