Implementation of Tizen SSO APIs

Implementation of SSO APIs as per widl file https://code.google.com/p/accounts-sso/source/browse/widl/signon.widl?repo=libgsignon-glib

Backend that provides core functionality is gSSO and more information about that
component could be found at https://01.org/gsso
Referring the chromium habit, you should rename the files:
* sso_authservice.[cc|h] -> sso_auth_service.[cc|h]
* sso_authsession.[cc|h] -> sso_auth_session.[cc|h]