Enable strict types everywhere (#1249)

lib/SimpleSAML/Auth/AuthenticationFactory.php

lib/SimpleSAML/Auth/DefaultAuth.php

lib/SimpleSAML/Auth/LDAP.php

lib/SimpleSAML/Auth/ProcessingChain.php

lib/SimpleSAML/Auth/ProcessingFilter.php

lib/SimpleSAML/Auth/Simple.php

lib/SimpleSAML/Auth/Source.php

lib/SimpleSAML/Auth/SourceFactory.php

lib/SimpleSAML/Auth/State.php

lib/SimpleSAML/Auth/TimeLimitedToken.php

lib/SimpleSAML/Bindings/Shib13/Artifact.php

lib/SimpleSAML/Bindings/Shib13/HTTPPost.php

lib/SimpleSAML/Configuration.php

lib/SimpleSAML/Database.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