Implemented test for ReplayedInResponseTo detection.
Work in progress on issue #31 - Validate InResponseTo

Implemented test Saml2Response_Validate_FalseOnMissingInResponseTo_IfDisallowed
Add config value for AllowUnsolicitedAuthnResponse
Add possibility to set AllowUnsolicitedAuthnResponse from code in tests
Implemented test Saml2Response_Validate_TrueOnMissingInResponseTo_IfAllowed