SAML2 federated authentication for ADFS.

Authentication workflow for the Active Directory Federated Services
(ADFS) by Microsoft is different from 'standard' ECP based one.
This plugin allows for authentication and fetching security token with SAML2
assertion inside, sending to the Service Provide and retrieving an
unscoped token.

Change-Id: I588de1967a7fb92c5928686d092895847553923a
Implements: blueprint add-saml2-cli-authentication
Merge "SAML2 federated authentication for ADFS."