Switch pkg packages, pub, and dartdoc to use package: imports.

pkg/logging/test/logging_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 logging_test;
 
-import '../../../pkg/logging/lib/logging.dart';
+import 'package:logging/logging.dart';
 import 'package:unittest/unittest.dart';
 
 main() {
   test('level comparison is a valid comparator', () {
     var level1 = const Level('NOT_REAL1', 253);
     expect(level1 == level1, isTrue);
     expect(level1 <= level1, isTrue);
     expect(level1 >= level1, isTrue);
     expect(level1 < level1, isFalse);
     expect(level1 > level1, isFalse);
@@ skipping 308 matching lines @@
             'SHOUT: 10']));
 
       expect(cMessages, equals([
             // 1 - 7 are lower in the hierarchy
             // 'FINE: 8' is not loggable
             'WARNING: 9',
             'SHOUT: 10']));
     });
   });
 }