implements #727
added reCaptcha to register section
feat #727
Added a boolean that enables or disables reCaptcha at user's registration form.
Merge remote-tracking branch 'origin/feat727'

Conflicts:
	config/locales/en/mconf.yml
	config/locales/pt-br/mconf.yml
Remove simple_captcha and some adjustments to recaptcha, refs #727

simple_captcha is not necessary anymore, was used in the registration only.
Also removed from SpacesController and JoinRequestsController code that
registered a new user (:shit:) and used simple_captcha.

recaptcha was not internationalized before, not it is.