Investigate the addition of a Single Sign On (SSO) solution

Migrated from: https://tracker.clearos.com/view.php?id=1873

Reported by: Marc Laporte

ClearOS's LDAP unified user & group system is fantastic. Users have the same credentials for all the apps (webmail, VPN, web apps, etc. whatever supports OpenLDAP)

However, users still need to login to each application. It's not as seamless as it could be. There are a few protocols to address this (SAML, CAS, etc.)

Related links:
https://www.openhub.net/p/phpcas
https://www.openhub.net/p/simplesamlphp
http://www.softwaresecured.com/2013/07/16/federated-identities-openid-vs-saml-vs-oauth/