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

tests/html/key_name_location_test.dart

-#library('KeyNameLocationTest');
-#import('../../pkg/unittest/unittest.dart');
-#import('../../pkg/unittest/html_config.dart');
-#import('dart:html');
+library KeyNameLocationTest;
+import '../../pkg/unittest/lib/unittest.dart';
+import '../../pkg/unittest/lib/html_config.dart';
+import 'dart:html';
 
 // Test for existence of some KeyName and KeyLocation constants.
 
 main() {
 
   useHtmlConfiguration();
 
   test('keyNames', () {
       expect(KeyName.DOWN_LEFT, "DownLeft");
       expect(KeyName.FN, "Fn");
       expect(KeyName.F1, "F1");
       expect(KeyName.META, "Meta");
       expect(KeyName.MEDIA_NEXT_TRACK, "MediaNextTrack");
       expect(KeyName.NUM_LOCK, "NumLock");
       expect(KeyName.PAGE_DOWN, "PageDown");
       expect(KeyName.DEAD_IOTA, "DeadIota");
   });
 
   test('keyLocations', () {
       expect(KeyLocation.STANDARD, 0);
       expect(KeyLocation.LEFT, 1);
       expect(KeyLocation.RIGHT, 2);
       expect(KeyLocation.NUMPAD, 3);
       expect(KeyLocation.MOBILE, 4);
       expect(KeyLocation.JOYSTICK, 5);
   });
 }