Create a SAML2 session during login

Create a SAML2 session during login

Use the updated session API to create a SAML2 session.
Note that each session is stored discretely. Previously if
a session for a provider already existed then that one session
held all the session indexes. Now if a new session comes in
it is added separately. During logout all sessions for a provider
are retrieved and all logged-in sessions sent to the SP to
log out.

https://fedorahosted.org/ipsilon/ticket/90

Signed-off-by: Rob Crittenden <rcritten@redhat.com>
Reviewed-by: Patrick Uiterwijk <puiterwijk@redhat.com>