Rebased from original master
Updated test XmlDocumentExtensions_Sign
- Now checks that a valid reference is used in the signing.
- Removed dangling param in xml comment causing compilation errors.
Minor fixes to Saml2ResponseTests.

- Readded an xml declaration that had been removed.
- Changed Status:Requester to Status:Success for all test messages containing assertions.
Cleanups to Saml2Response
- Removed this prefix for member access.
- Made allAssertionElementNodes lazily evaluated.
Merge pull request #51 from AndersAbel/39SignValFixed

Cleaned up version of #39 Extended signature validation to support signed assertions
Removed mention of HuBoard.
- We'll stick to plain github issue management for now.
Added test skeletons for InResponseTo.
Added positive test for InReseponseTo.
Work in progress on issue #31 - Validate InResponseTo
Add PendingAuthnRequests helper to keep track of issued AuthnRequest id's.
Start testing validation of InResponseTo
Changed PendingAuthnRequests to have a TryRemove method instead of Remove.
Checks InResponseTo if existing.
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
Fixed #31.

Implemented test Saml2Response_Validate_FalseOnReplyFromWrongIdp
Changed XML-structure in all responses in test data to have Issue as an element instead of an attribute, according to SAML2-specification.
Changed PendingAuthnRequests to also contain info about IDP
ValidateInResponseTo: Changed config lookup of AllwounsolicitedAuthnResponse to look for the IDP specified in the Issuer field instead of the first config.
Added my self to the contributors file
Fixed #31

Refactor text XML data to put the xmlns:saml2=""urn:oasis:names:tc:SAML:2.0:assertion"" in the top of the documents to avoid duplicate namespace definitions
Fixed old tests after rebase.
Modified test initialize method to store config value for AllowUnsolicitedResponse before setting the initial value.

Added TestCleanUp method to restore config value for AllowUnsolicitedResponse.
Signatures must have exactly one reference.
- Added test case for multiple signatures
- Adjusted code to fail validation on multiple signatures.
- Fixes #54.