Add email_verified mapper configuration (required)

A couple of improvements suggested for the SSO for admin portal documentation based on tcorcora@redhat.com's comments here https://issues.jboss.org/browse/THREESCALE-225?focusedCommentId=13431390&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-13431390

1) Document what's needed for Admin SSO on the page itself: https://support.3scale.net/docs/accounts/admin-portal-sso rather than delegating some to the Dev Portal SSO documentation page. The Dev Portal page includes info on the email_verified mapper (my bad it's there) but also talks about org_name - which is not applicable. Leads one to believe the whole mapping section is not applicable to admin SSO.
Dev Portal SSO doc also talks about adding the URL: https://yourdomain.3scale.net
This is not applicable for the admin portal - should be https://yourdomain-*_admin_*.3scale.net
2) Is sentence at the end right?:_ If necessary, complete sign up by entering any needed information_
I wasn't prompted to sign up....