Use JS recaptcha lib in signup instead of image returned by WS

Setting up the site To test this issue, you need a site with  MDL-61600 applied. In web as admin, set up site reCAPTCHA keys (Site administration > Plugins > Authentication > Manage authentication). You can request the keys in here . Enable Email-based self-registration (Site administration > Plugins > Authentication > Manage authentication) Enable reCAPTCHA for Email-based self-registration (Site administration > Plugins > Authentication > Email-based self-registration) Go to Site administration > Security > HTTP security and enable "Allow frame embedding". Finally, create a new feedback and add a Captcha question. Testing the issue In the app, click to add a new site and enter the site URL. In the credentials page, click to create a new account. Check that you see an "Answer" button in the security question category.  Fill all the fields except the Captcha (security question). Click to send the form and check that you see an error message. Now click the "Answer" button in the security question category and check that a modal is opened with the recaptcha element. Answer the recaptcha (the modal should be closed automatically) and send the form again. Check that now the form is successfully submitted. Now login in the site and open the feedback created before (the one with the captcha). Check that the captcha works fine in there too.