Move a bunch of src/ files into subdirectories.

lib/src/configuration.dart

-// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-library unittest.configuration;
-
-import 'test_case.dart';
-
-/// This is a stub class used to preserve compatibility with unittest 0.11.*.
-///
-/// It will be removed before the next version is released.
-@deprecated
-class Configuration {
-  Configuration();
-  Configuration.blank();
-
-  final autoStart = true;
-  Duration timeout = const Duration(minutes: 2);
-  void onInit() {}
-  void onStart() {}
-  void onTestStart(TestCase testCase) {}
-  void onTestResult(TestCase testCase) {}
-  void onTestResultChanged(TestCase testCase) {}
-  void onLogMessage(TestCase testCase, String message) {}
-  void onDone(bool success) {}
-  void onSummary(int passed, int failed, int errors, List<TestCase> results,
-      String uncaughtError) {}
-}