Restructure pkg/unittest and pkg/webdriver to follow the pub conventions.

tests/html/selectelement_test.dart

 // Copyright (c) 2012, 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('selectelement_test');
-#import('../../pkg/unittest/unittest.dart');
-#import('../../pkg/unittest/html_config.dart');
-#import('dart:html');
+library selectelement_test;
+import '../../pkg/unittest/lib/unittest.dart';
+import '../../pkg/unittest/lib/html_config.dart';
+import 'dart:html';
 
 main() {
   useHtmlConfiguration();
 
   test('selectedOptions', () {
     var element = new SelectElement();
     element.multiple = false;
     var options = [
       new OptionElement(),
       new DivElement(),
@@ skipping 30 matching lines @@
       new OptionElement(),
       new OptionElement('data', 'two', false, true),
       new OptionElement('data', 'two', false, true),
       new OptionElement(),
     ];
     element.elements.addAll(options);
     // Use last to make sure that the list was correctly wrapped.
     expect(element.options.last, equals(options[3]));
   });
 }