Replace SimpleSAML_Error_* with namespaced version

config-templates/config.php

lib/SimpleSAML/Auth/LDAP.php

lib/SimpleSAML/Auth/ProcessingChain.php

lib/SimpleSAML/Auth/Simple.php

lib/SimpleSAML/Auth/Source.php

lib/SimpleSAML/Auth/State.php

lib/SimpleSAML/Bindings/Shib13/Artifact.php

lib/SimpleSAML/Configuration.php

lib/SimpleSAML/Error/Assertion.php

lib/SimpleSAML/Error/AuthSource.php

lib/SimpleSAML/Error/BadRequest.php

lib/SimpleSAML/Error/BadUserInput.php

lib/SimpleSAML/Error/CannotSetCookie.php

lib/SimpleSAML/Error/ConfigurationError.php

lib/SimpleSAML/Error/CriticalConfigurationError.php

lib/SimpleSAML/Error/Error.php

lib/SimpleSAML/Error/ErrorCodes.php

lib/SimpleSAML/Error/Exception.php

lib/SimpleSAML/Error/InvalidCredential.php

lib/SimpleSAML/Error/MetadataNotFound.php