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

tests/html/inner_frame_test.dart

-#library('InnerFrameTest');
-#import('../../pkg/unittest/unittest.dart');
-#import('../../pkg/unittest/html_config.dart');
-#import('dart:html');
+library InnerFrameTest;
+import '../../pkg/unittest/lib/unittest.dart';
+import '../../pkg/unittest/lib/html_config.dart';
+import 'dart:html';
 
 main() {
   if (window != window.top) {
     // Child frame.
 
     // The child's frame should not be able to access its parent's
     // document.
 
     window.on.message.add((Event e) {
       switch (e.data) {
@@ skipping 96 matching lines @@
 
   test('parent', () {
       validate('parent', () {
         var div = document.query('#illegalParent');
 
         // Ensure that this parent frame was not modified by its child.
         expect(div, isNull);
       });
     });
 }