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

tests/html/indexeddb_1_test.dart

-#library('IndexedDB1Test');
-#import('../../pkg/unittest/unittest.dart');
-#import('../../pkg/unittest/html_config.dart');
-#import('dart:html');
+library IndexedDB1Test;
+import '../../pkg/unittest/lib/unittest.dart';
+import '../../pkg/unittest/lib/html_config.dart';
+import 'dart:html';
 
 const String DB_NAME = 'Test';
 const String STORE_NAME = 'TEST';
 const int VERSION = 1;
 
 testReadWrite(key, value, matcher,
               [dbName = DB_NAME,
                storeName = STORE_NAME,
                version = VERSION]) => () {
   var db;
@@ skipping 157 matching lines @@
   test('test3', testReadWriteTyped(123, [1, 2, 3], equals([1, 2, 3])));
   test('test4', testReadWriteTyped(123, [2, 3, 4], equals([2, 3, 4])));
 }
 
 main() {
   useHtmlConfiguration();
 
   tests_dynamic();
   tests_typed();
 }