Sylvia/docs/doc 1105

@lamagnifica @catong @mhoeber: This is a draft of the updates to the Register Your Account section to reflect the new login/registration page. The feature is currently in a/b testing, so we don't want to merge the branch yet, but feedback is still welcome.
The above text was taken directly from the email, and I'm not sure who's in charge of it. I just took it out of the docs here since we don't really need it and it might change again without warning.