Rename the _fletch_system and service and dart: libraries

lib/collection/collection_patch.dart

 // Copyright (c) 2015, the Fletch 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.md file.
 
-import 'dart:_fletch_system' as fletch;
+import 'dart:fletch._system' as fletch;
 
 const patch = "patch";
 
 @patch class HashMap<K, V> {
   @patch factory HashMap({ bool equals(K key1, K key2),
                            int hashCode(K key),
                            bool isValidKey(potentialKey) }) {
     if (isValidKey == null) {
       if (hashCode == null) {
         if (equals == null) {
@@ skipping 1396 matching lines @@
   E lookup(Object o) => _validKey(o) ? super.lookup(o) : null;
   bool remove(Object o) => _validKey(o) ? super.remove(o) : false;
 
   _CompactLinkedCustomHashSet(this._equality, this._hasher, validKey)
       : _validKey = (validKey != null) ? validKey : _defaultTypeTest;
 
   Set<E> toSet() =>
       new _CompactLinkedCustomHashSet<E>(_equality, _hasher, _validKey)
           ..addAll(this);
 }