Instead of keeping SAML-specific error exceptions in lib/SimpleSAML/Error, it makes more sense to have those in the saml module. Now that we have the recent NoAvailableIDP and NoSupportedIDP errors moved there, it's time to change the code implemented recently that uses them.

- Bugfix: the modules/saml/www/proxy/invalid_session.php shouldn't call directly the error handler in sspmod_saml_IdP_SAML2. Instead, it should use the SimpleSAML_Auth_State::throwException() method to let it handle the exception appropriately (in this case, it should always return back to the requester).
- The standard specifies that a "urn:oasis:names:tc:SAML:2.0:status:NoSupportedIDP" or "urn:oasis:names:tc:SAML:2.0:status:NoAvailableIDP" second-level status code should be returned to the requester in case an error occurs. Add a couple of exceptions to represent both statuses, and use them to set the right status code in the response.
- We shouldn't ask the user to logout in case the IDPList does not offer an IdP we recognize, or in case the proxy enforces the use of an IdP ('idp' configuration option in the auth source) and such IdP is in the IDPList.
- Similarly, these two cases should also handled in case we are authenticating for the first time, not only when reauthenticating.

Now we are finally using the 2.x branch of the SAML2 library, which was also migrated to use namespaces. Even though the library provides an autoloader that allows loading the classes with the old names using class aliasing, we need to do the migration in one commit (at least for most part of it). This is due to the way SimpleSAMLphp checks data types, using inheritance to check objects agains abstract or more general classes. Even though class aliasing works, there's no way to replicate those relationships, and type checks that use the old class names will fail because the aliases are virtually new classes that don't inherit from others.

(being respectful with occurences that might change the behaviour, i.e. default database prefixes)

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@2374 44740490-163a-0410-bde0-09ae8108e29a

AuthenticatingAuthority and RequesterID.


git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@2278 44740490-163a-0410-bde0-09ae8108e29a

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@1597 44740490-163a-0410-bde0-09ae8108e29a

Introduce a new class: sspmod_saml2_Error, which represents
SAML 2 status codes.

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@1570 44740490-163a-0410-bde0-09ae8108e29a