Comment 12 for bug 1252098

Okay, I refactored the "captcha" element into a pieform element and added support for internationalization to it. This is still a minor change but in order to keep the commits well-formed I've split it into 5 parts. They're all tagged under topic "recaptcha": https://reviews.mahara.org/#/q/status:open+project:mahara+branch:master+topic:recaptcha,n,z

1. https://reviews.mahara.org/3062 - Alters Pieforms to add a hook for a pieform element to remove itself from Pieforms (so that the captcha pieform element won't display unless captchas are enabled)

2. https://reviews.mahara.org/3055 - Adding the recaptcha 3rd party library

3. https://reviews.mahara.org/3056 - Patching the recaptcha 3rd party library to use protocol-relative URLs

4. https://reviews.mahara.org/3062 - Patching the rectapcha 3rd party library to use Mahara's current language

3. https://reviews.mahara.org/3054 - Defining the "captcha" pieform element and adding it to the user registration page