Made Saml2PSecurityTokenHandler part of the SP options.
- The Saml2PSecurityTokenHandler instance is dependent on the EntityId of the SP, so a default static instance won't do any more.
- The handler must be kept alive between calls for the replay detection to work, so adding it to options.
- Removed the default, static instance of Saml2PSecurityTokenHandler.
- Added spOptions parameter to Saml2Response.CreateClaims and updated all tests.