Interoporability issues in SAML 2.0 implementation

In the current SAML 2.0 implementation, there are two places which cause some interoperability issues with other implementations.

1. It should use generic SubjectConfirmationElement when processing the assertion.
2. Attributes "NotBefore" and "NotOnOrAfter" should be set in a Conditions element. Currently it is set in the SubjectConfirmationData element, which defines validity period only for the Subject element, not the entire assertion.